Catalan numbers

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Catalan numbers
You are encouraged to solve this task according to the task description, using any language you may know.

Catalan numbers are a sequence of numbers which can be defined directly:

${\displaystyle C_{n}={\frac {1}{n+1}}{2n \choose n}={\frac {(2n)!}{(n+1)!\,n!}}\qquad {\mbox{ for }}n\geq 0.}$

Or recursively:

${\displaystyle C_{0}=1\quad {\mbox{and}}\quad C_{n+1}=\sum _{i=0}^{n}C_{i}\,C_{n-i}\quad {\text{for }}n\geq 0;}$

Or alternatively (also recursive):

${\displaystyle C_{0}=1\quad {\mbox{and}}\quad C_{n}={\frac {2(2n-1)}{n+1}}C_{n-1},}$

Implement at least one of these algorithms and print out the first 15 Catalan numbers with each.

Memoization   is not required, but may be worth the effort when using the second method above.

11l

V c = 1
L(n) 1..15
print(c)
c = 2 * (2 * n - 1) * c I/ (n + 1)
Output:
1
1
2
5
14
42
132
429
1430
4862
16796
58786
208012
742900
2674440


360 Assembly

Very compact version.

CATALAN  CSECT        08/09/2015
USING  CATALAN,R15
LA     R7,1               c=1
LA     R6,1               i=1
LOOPI    CH     R6,=H'15'          do i=1 to 15
BH     ELOOPI
XDECO  R6,PG              edit i
LR     R5,R6              i
SLA    R5,1               *2
BCTR   R5,0               -1
SLA    R5,1               *2
MR     R4,R7              *c
LA     R6,1(R6)           i=i+1
DR     R4,R6              /i
LR     R7,R5              c=2*(2*i-1)*c/(i+1)
XDECO  R7,PG+12           edit c
XPRNT  PG,24              print
B      LOOPI              next i
ELOOPI   BR     R14
PG       DS     CL24
YREGS
END    CATALAN
Output:
           1           1
2           2
3           5
4          14
5          42
6         132
7         429
8        1430
9        4862
10       16796
11       58786
12      208012
13      742900
14     2674440
15     9694845


ABAP

This works for ABAP Version 7.40 and above

report z_catalan_numbers.

class catalan_numbers definition.
public section.
class-methods:
get_nth_number
importing
i_n                     type int4
returning
value(r_catalan_number) type int4.
endclass.

class catalan_numbers implementation.
method get_nth_number.
r_catalan_number = cond int4(
when i_n eq 0
then 1
else reduce int4(
init
result = 1
index = 1
for position = 1 while position <= i_n
next
result = result * 2 * ( 2 * index - 1 ) div ( index + 1 )
index = index + 1 ) ).
endmethod.
endclass.

start-of-selection.
do 15 times.
write / |C({ sy-index - 1 }) = { catalan_numbers=>get_nth_number( sy-index - 1 ) }|.
enddo.

Output:
C(0) = 1
C(1) = 1
C(2) = 2
C(3) = 5
C(4) = 14
C(5) = 42
C(6) = 132
C(7) = 429
C(8) = 1430
C(9) = 4862
C(10) = 16796
C(11) = 58786
C(12) = 208012
C(13) = 742900
C(14) = 2674440


Action!

INCLUDE "D2:REAL.ACT" ;from the Action! Tool Ki

PROC Main()
REAL c,rnom,rden
BYTE n,nom,den

Put(125) PutE() ;clear the screen
IntToReal(1,c)

FOR n=1 TO 15
DO
nom=(n LSH 1-1) LSH 1
den=n+1
IntToReal(nom,rnom)
IntToReal(den,rden)
RealMult(c,rnom,c)
RealDiv(c,rden,c)
PrintF("C(%B)=",n) PrintRE(c)
OD
RETURN
Output:
C(1)=1
C(2)=2
C(3)=5
C(4)=14
C(5)=42
C(6)=132
C(7)=429
C(8)=1430
C(9)=4862
C(10)=16796
C(11)=58786
C(12)=208012
C(13)=742900
C(14)=2674440
C(15)=9694845


with Ada.Text_IO;  use Ada.Text_IO;

procedure Test_Catalan is
function Catalan (N : Natural) return Natural is
Result : Positive := 1;
begin
for I in 1..N loop
Result := Result * 2 * (2 * I - 1) / (I + 1);
end loop;
return Result;
end Catalan;
begin
for N in 0..15 loop
Put_Line (Integer'Image (N) & " =" & Integer'Image (Catalan (N)));
end loop;
end Test_Catalan;

Sample output:
 0 = 1
1 = 1
2 = 2
3 = 5
4 = 14
5 = 42
6 = 132
7 = 429
8 = 1430
9 = 4862
10 = 16796
11 = 58786
12 = 208012
13 = 742900
14 = 2674440
15 = 9694845


ALGOL 68

# calculate the first few catalan numbers, using LONG INT values        #
# (64-bit quantities in Algol 68G which can handle up to C23)           #

# returns n!/k!                                                         #
PROC factorial over factorial = ( INT n, k )LONG INT:
IF      k > n THEN 0
ELIF    k = n THEN 1
ELSE #  k < n #
LONG INT f := 1;
FOR i FROM k + 1 TO n DO f *:= i OD;
f
FI # factorial over factorial # ;

# returns n!                                                             #
PROC factorial = ( INT n )LONG INT:
BEGIN
LONG INT f := 1;
FOR i FROM 2 TO n DO f *:= i OD;
f
END # factorial # ;

# returnss the nth Catalan number using binomial coefficeients            #
# uses the factorial over factorial procedure for a slight optimisation   #
# note:     Cn = 1/(n+1)(2n n)                                            #
#              = (2n)!/((n+1)!n!)                                         #
#              = factorial over factorial( 2n, n+1 )/n!                   #
PROC catalan = ( INT n )LONG INT: IF n < 2 THEN 1 ELSE factorial over factorial( n + n, n + 1 ) OVER factorial( n ) FI;

# show the first few catalan numbers                                      #
FOR i FROM 0 TO 15 DO
print( ( whole( i, -2 ), ": ", whole( catalan( i ), 0 ), newline ) )
OD
Output:
 0: 1
1: 1
2: 2
3: 5
4: 14
5: 42
6: 132
7: 429
8: 1430
9: 4862
10: 16796
11: 58786
12: 208012
13: 742900
14: 2674440
15: 9694845


ALGOL W

begin
% print the catalan numbers up to C15 %
integer Cprev;
Cprev := 1; % C0 %
write(     s_w := 0, i_w := 3, 0, ": ", i_w := 9, Cprev );
for n := 1 until 15 do begin
Cprev := round( ( ( ( 4 * n ) - 2 ) / ( n + 1 ) ) * Cprev );
write( s_w := 0, i_w := 3, n, ": ", i_w := 9, Cprev );
end for_n
end.
Output:
  0:         1
1:         1
2:         2
3:         5
4:        14
5:        42
6:       132
7:       429
8:      1430
9:      4862
10:     16796
11:     58786
12:    208012
13:    742900
14:   2674440
15:   9694845


APL

      {(!2×⍵)÷(!⍵+1)×!⍵}(⍳15)-1

Output:
1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440

Arturo

catalan: function [n][
if? n=0 -> 1
else 	-> div (catalan n-1) * (4*n)-2 n+1
]

loop 0..15 [i][
print [
pad.left to :string catalan i 20
]
]

Output:
0                        1
1                        1
2                        2
3                        5
4                       14
5                       42
6                      132
7                      429
8                     1430
9                     4862
10                   16796
11                   58786
12                  208012
13                  742900
14                 2674440
15                 9694845

AutoHotkey

As AutoHotkey has no BigInt, the formula had to be tweaked to prevent overflow. It still fails after n=22

Loop 15
out .= "n" Catalan(A_Index)
Msgbox % clipboard := SubStr(out, 2)
catalan( n ) {
; By [VxE]. Returns ((2n)! / ((n + 1)! * n!)) if 0 <= N <= 22 (higher than 22 results in overflow)
If ( n < 3 ) ; values less than 3 are handled specially
Return n < 0 ? "" : n = 0 ? 1 : n

i := 1 ; initialize the accumulator to 1

Loop % n - 1 >> 1 ; build the numerator by multiplying odd values between 2N and N+1
i *= 1 + ( n - A_Index << 1 )

i <<= ( n - 2 >> 1 ) ; multiply the numerator by powers of 2 according to N

Loop % n - 3 >> 1 ; finish up by (integer) dividing by each of the non-cancelling factors
i //= A_Index + 2

Return i
}

Output:
1
2
5
14
42
132
429
1430
4862
16796
58786
208012
742900
2674440
9694845

AWK

# syntax: GAWK -f CATALAN_NUMBERS.AWK
BEGIN {
for (i=0; i<=15; i++) {
printf("%2d %10d\n",i,catalan(i))
}
exit(0)
}
function catalan(n,  ans) {
if (n == 0) {
ans = 1
}
else {
ans = ((2*(2*n-1))/(n+1))*catalan(n-1)
}
return(ans)
}

Output:
 0          1
1          1
2          2
3          5
4         14
5         42
6        132
7        429
8       1430
9       4862
10      16796
11      58786
12     208012
13     742900
14    2674440
15    9694845


BASIC

Works with: FreeBASIC
Works with: QuickBASIC version 4.5 (untested)

Use of REDIM PRESERVE means this will not work in QBasic (although that could be worked around if desired).

DECLARE FUNCTION catalan (n as INTEGER) AS SINGLE

REDIM SHARED results(0) AS SINGLE

FOR x% = 1 TO 15
PRINT x%, catalan (x%)
NEXT

FUNCTION catalan (n as INTEGER) AS SINGLE
IF UBOUND(results) < n THEN REDIM PRESERVE results(n)

IF 0 = n THEN
results(0) = 1
ELSE
results(n) = ((2 * ((2 * n) - 1)) / (n + 1)) * catalan(n - 1)
END IF
catalan = results(n)
END FUNCTION

Output:
1             1
2             2
3             5
4             14
5             42
6             132
7             429
8             1430
9             4862
10            16796
11            58786
12            208012
13            742900
14            2674440
15            9694845


Applesoft BASIC

Works with: Chipmunk Basic
Works with: QBasic
10 HOME : REM  10 CLS for Chipmunk Basic/QBasic
20 DIM c(15)
30 c(0) = 1
40 PRINT 0, c(0)
50 FOR n = 0 TO 14
60   c(n + 1) = 0
70   FOR i = 0 TO n
80     c(n + 1) = c(n + 1) + c(i) * c(n - i)
90   NEXT i
100   PRINT n + 1, c(n + 1)
110 NEXT n
120 END


BASIC256

Translation of: FreeBASIC
function factorial(n)
if n = 0 then return 1
return n * factorial(n - 1)
end function

function catalan1(n)
prod = 1
for i = n + 2 to 2 * n
prod *= i
next i
return int(prod / factorial(n))
end function

function catalan2(n)
if n = 0 then return 1
sum = 0
for i = 0 to n - 1
sum += catalan2(i) * catalan2(n - 1 - i)
next i
return sum
end function

function catalan3(n)
if n = 0 then return 1
return catalan3(n - 1) * 2 * (2 * n - 1) \ (n + 1)
end function

print "n", "First", "Second", "Third"
print "-", "-----", "------", "-----"
print
for i = 0 to 15
print i,  catalan1(i), catalan2(i), catalan3(i)
next i

Output:
Same as FreeBASIC entry.

BBC BASIC

      10 FOR i% = 1 TO 15
20   PRINT FNcatalan(i%)
30 NEXT
40 END
50 DEF FNcatalan(n%)
60   IF n% = 0 THEN = 1
70   = 2 * (2 * n% - 1) * FNcatalan(n% - 1) / (n% + 1)

Output:
         1
1
2
5
14
42
132
429
1430
4862
16796
58786
208012
742900
2674440

Chipmunk Basic

Works with: Chipmunk Basic version 3.6.4
Translation of: Run BASIC
10 FOR i = 1 TO 15
20   PRINT i;" ";catalan(i)
30 NEXT
40 END
50 SUB catalan(n)
60   catalan = 1
70   IF n <> 0 THEN catalan = ((2*((2*n)-1))/(n+1))*catalan(n-1)
80 END SUB


Craft Basic

dim c[16]

let c[0] = 1

for n = 0 to 15

let p = n + 1
let c[p] = 0

for i = 0 to n

let q = n - i
let c[p] = c[p] + c[i] * c[q]

next i

print n, " ", c[n]

next n

Output:

0 1
1 1
2 2
3 5
4 14
5 42
6 132
7 429
8 1430
9 4862
10 16796
11 58786
12 208012
13 742900
14 2674440
15 9694845



FreeBASIC

' FB 1.05.0 Win64

Function factorial(n As UInteger) As UInteger
If n = 0 Then Return 1
Return n * factorial(n - 1)
End Function

Function catalan1(n As UInteger) As UInteger
Dim prod As UInteger = 1
For i As UInteger = n + 2 To 2 * n
prod *= i
Next
Return prod / factorial(n)
End Function

Function catalan2(n As UInteger) As UInteger
If n = 0 Then Return 1
Dim sum As UInteger = 0
For i As UInteger = 0 To n - 1
sum += catalan2(i) * catalan2(n - 1 - i)
Next
Return sum
End Function

Function catalan3(n As UInteger) As UInteger
If n = 0 Then Return 1
Return catalan3(n - 1) * 2 * (2 * n - 1) \ (n + 1)
End Function

Print "n", "First", "Second", "Third"
Print "-", "-----", "------", "-----"
Print
For i As UInteger = 0 To 15
Print i,  catalan1(i), catalan2(i), catalan3(i)
Next
Print
Print "Press any key to quit"
Sleep

Output:
n             First         Second        Third
-             -----         ------        -----

0             1             1             1
1             1             1             1
2             2             2             2
3             5             5             5
4             14            14            14
5             42            42            42
6             132           132           132
7             429           429           429
8             1430          1430          1430
9             4862          4862          4862
10            16796         16796         16796
11            58786         58786         58786
12            208012        208012        208012
13            742900        742900        742900
14            2674440       2674440       2674440
15            9694845       9694845       9694845


FutureBasic

Translation of: FreeBASIC
include "NSLog.incl"

local fn Factorial( n as NSInteger ) as UInt64
UInt64 sum = 0

if n = 0 then sum = 1 : exit fn
sum = n * fn Factorial( n - 1 )
end fn = sum

local fn Catalan1( n as NSInteger ) as UInt64
UInt64     product = 1, result
NSUInteger i

for i = n + 2 to 2 * n
product = product * i
next
result = product / fn Factorial( n )
end fn = result

local fn Catalan2( n as NSInteger ) as UInt64
UInt64     sum = 0
NSUInteger i

if n = 0 then sum = 1 : exit fn
for i = 0 to n - 1
sum += fn Catalan2(i) * fn Catalan2( n - 1 - i )
next
end fn = sum

local fn Catalan3( n as NSInteger ) as UInt64
UInt64 result

if n = 0 then result = 1 : exit fn
result = fn Catalan3( n - 1 ) * 2 * ( 2 * n - 1 ) / ( n + 1 )
end fn = result

NSUInteger i

for i = 0 to 19
if( i < 16 )
NSLog( @"%3d.\t\t%7llu\t\t%12llu\t\t%12llu", i, fn Catalan1( i ), fn Catalan2( i ), fn Catalan3( i ) )
else
NSLog( @"%3d.\t\t%@\t\t%12llu\t\t%12llu", i, @"[-err-]", fn Catalan2( i ), fn Catalan3( i ) )
end if
next

HandleEvents
Output:
  0.		      1		           1		           1
1.		      1		           1		           1
2.		      2		           2		           2
3.		      5		           5		           5
4.		     14		          14		          14
5.		     42		          42		          42
6.		    132		         132		         132
7.		    429		         429		         429
8.		   1430		        1430		        1430
9.		   4862		        4862		        4862
10.		  16796		       16796		       16796
11.		  58786		       58786		       58786
12.		 208012		      208012		      208012
13.		 742900		      742900		      742900
14.		2674440		     2674440		     2674440
15.		9694845		     9694845		     9694845
16.		[-err-]		    35357670		    35357670
17.		[-err-]		   129644790		   129644790
18.		[-err-]		   477638700		   477638700
19.		[-err-]		  1767263190		  1767263190


GW-BASIC

Works with: BASICA
100 REM Catalan numbers
110 DIM C(15)
120 C(0) = 1
130 PRINT 0, C(0)
140 FOR N = 0 TO 14
150  C(N + 1) = 0
160  FOR I = 0 TO N
170   C(N + 1) = C(N + 1) + C(I) * C(N - I)
180  NEXT I
190  PRINT N + 1, C(N + 1)
200 NEXT N
210 END

Output:
 0             1
1             1
2             2
3             5
4             14
5             42
6             132
7             429
8             1430
9             4862
10            16796
11            58786
12            208012
13            742900
14            2674440
15            9694845


Liberty BASIC

Works with: Just BASIC
print "non-recursive version"
print catNonRec(5)
for i = 0 to 15
print i;"   =   "; catNonRec(i)
next
print

print "recursive version"
print catRec(5)
for i = 0 to 15
print i;"   =   "; catRec(i)
next
print

print "recursive with memoisation"
redim cats(20)  'clear the array
print catRecMemo(5)
for i = 0 to 15
print i;"   =   "; catRecMemo(i)
next
print

wait

function catNonRec(n)   'non-recursive version
catNonRec=1
for i=1 to n
catNonRec=((2*((2*i)-1))/(i+1))*catNonRec
next
end function

function catRec(n)  'recursive version
if n=0 then
catRec=1
else
catRec=((2*((2*n)-1))/(n+1))*catRec(n-1)
end if
end function

function catRecMemo(n)  'recursive version with memoisation
if n=0 then
catRecMemo=1
else
if cats(n-1)=0 then    'call it recursively only if not already calculated
prev = catRecMemo(n-1)
else
prev = cats(n-1)
end if
catRecMemo=((2*((2*n)-1))/(n+1))*prev
end if
cats(n) = catRecMemo    'memoisation for future use
end function
Output:
non-recursive version
42
0   =   1
1   =   1
2   =   2
3   =   5
4   =   14
5   =   42
6   =   132
7   =   429
8   =   1430
9   =   4862
10   =   16796
11   =   58786
12   =   208012
13   =   742900
14   =   2674440
15   =   9694845

recursive version
42
0   =   1
1   =   1
2   =   2
3   =   5
4   =   14
5   =   42
6   =   132
7   =   429
8   =   1430
9   =   4862
10   =   16796
11   =   58786
12   =   208012
13   =   742900
14   =   2674440
15   =   9694845

recursive with memoisation
42
0   =   1
1   =   1
2   =   2
3   =   5
4   =   14
5   =   42
6   =   132
7   =   429
8   =   1430
9   =   4862
10   =   16796
11   =   58786
12   =   208012
13   =   742900
14   =   2674440
15   =   9694845

Minimal BASIC

Translation of: GW-BASIC
10 REM Catalan numbers
20 DIM C(15)
30 LET C(0) = 1
40 PRINT 0, C(0)
50 FOR N = 0 TO 14
60 LET C(N+1) = 0
70 FOR I = 0 TO N
80 LET C(N+1) = C(N+1)+C(I)*C(N-I)
90 NEXT I
100 PRINT N+1, C(N+1)
110 NEXT N
120 END


PureBasic

Using the third formula...

; saving the division for last ensures we divide the largest
; numerator by the smallest denominator

Procedure.q CatalanNumber(n.q)
If n<0:ProcedureReturn 0:EndIf
If n=0:ProcedureReturn 1:EndIf
ProcedureReturn (2*(2*n-1))*CatalanNumber(n-1)/(n+1)
EndProcedure

ls=25
rs=12

a.s=""
a.s+LSet(RSet("n",rs),ls)+"CatalanNumber(n)"
; cw(a.s)
Debug a.s

For n=0 to 33 ;33 largest correct quad for n
a.s=""
a.s+LSet(RSet(Str(n),rs),ls)+Str(CatalanNumber(n))
; cw(a.s)
Debug a.s
Next

Sample Output:
           n             CatalanNumber(n)
0             1
1             1
2             2
3             5
4             14
5             42
6             132
7             429
8             1430
9             4862
10             16796
11             58786
12             208012
13             742900
14             2674440
15             9694845
16             35357670
17             129644790
18             477638700
19             1767263190
20             6564120420
21             24466267020
22             91482563640
23             343059613650
24             1289904147324
25             4861946401452
26             18367353072152
27             69533550916004
28             263747951750360
29             1002242216651368
30             3814986502092304
31             14544636039226909
32             55534064877048198
33             212336130412243110


Run BASIC

FOR i = 1 TO 15
PRINT i;" ";catalan(i)
NEXT

FUNCTION catalan(n)
catalan = 1
if n <> 0 then catalan = ((2 * ((2 * n) - 1)) / (n + 1)) * catalan(n - 1)
END FUNCTION
1 1
2 2
3 5
4 14
5 42
6 132
7 429
8 1430
9 4862
10 16796
11 58786
12 208012
13 742900
14 2674440
15 9694845

Sinclair ZX81 BASIC

Works with 1k of RAM.

The specification asks for the first 15 Catalan numbers. A lot of the other implementations produce either C(0) to C(15), which is 16 numbers, or else C(1) to C(15)—which is 15 numbers, but I'm not convinced they're the first 15. This program produces C(0) to C(14).

 10 FOR N=0 TO 14
20 LET X=N
30 GOSUB 130
40 LET A=FX
50 LET X=N+1
60 GOSUB 130
70 LET B=FX
80 LET X=2*N
90 GOSUB 130
100 PRINT N,FX/(B*A)
110 NEXT N
120 STOP
130 LET FX=1
140 FOR I=1 TO X
150 LET FX=FX*I
160 NEXT I
170 RETURN

Output:
0               1
1               1
2               2
3               5
4               14
5               42
6               132
7               429
8               1430
9               4862
10              16796
11              58786
12              208012
13              742900
14              2674440

smart BASIC

PRINT "Recursive:"!PRINT
FOR n = 0 TO 15
PRINT n,"#######":catrec(n)
NEXT n
PRINT!PRINT

PRINT "Non-recursive:"!PRINT
FOR n = 0 TO 15
PRINT n,"#######":catnonrec(n)
NEXT n

END

DEF catrec(x)
IF x = 0 THEN
temp = 1
ELSE
n = x
temp = ((2*((2*n)-1))/(n+1))*catrec(n-1)
END IF
catrec = temp
END DEF

DEF catnonrec(x)
temp = 1
FOR n = 1 TO x
temp = (2*((2*n)-1))/(n+1)*temp
NEXT n
catnonrec = temp
END DEF


TI-83 BASIC

This problem is perfectly suited for a TI calculator.

:For(I,1,15
:Disp (2I)!/((I+1)!I!
:End
Output:
               1
2
4
14
42
132
429
1430
4862
16796
58786
208012
742900
2674440
9694845
Done

Tiny BASIC

Integers are limited to 32767 so only the first ten Catalan numbers can be represented. And even then one has to do some finagling to avoid internal overflows.

Works with: TinyBasic
10 REM Catalan numbers
20 LET N = 0
30 LET C = 1
40 PRINT N," ",C
50 IF N > 9 THEN END
60 LET N = N + 1
70 GOSUB 200
80 LET C = (2 * N - 1) * C
90 LET C = 2 * C / (N + 1)
100 LET C = C + 2 * I * (2 * N - 1)
110 GOTO 40
200 LET I = 0
210 IF C <= 0 THEN RETURN
220 LET C = C - (N + 1)
230 LET I = I + 1
240 GOTO 210
250 REM To avoid internal overflow, I subtract something clever from
260 REM C and then add it back at the end.

Output:
0               1
1               1
2               2
3               5
4               14
5               42
6               132
7               429
8               1430
9               4862
10              16796

VBA

Public Sub Catalan1(n As Integer)
'Computes the first n Catalan numbers according to the first recursion given
Dim Cat() As Long
Dim sum As Long

ReDim Cat(n)
Cat(0) = 1
For i = 0 To n - 1
sum = 0
For j = 0 To i
sum = sum + Cat(j) * Cat(i - j)
Next j
Cat(i + 1) = sum
Next i
Debug.Print
For i = 0 To n
Debug.Print i, Cat(i)
Next
End Sub

Public Sub Catalan2(n As Integer)
'Computes the first n Catalan numbers according to the second recursion given
Dim Cat() As Long

ReDim Cat(n)
Cat(0) = 1
For i = 1 To n
Cat(i) = 2 * Cat(i - 1) * (2 * i - 1) / (i + 1)
Next i
Debug.Print
For i = 0 To n
Debug.Print i, Cat(i)
Next
End Sub

Result:
Catalan1 15

0             1
1             1
2             2
3             5
4             14
5             42
6             132
7             429
8             1430
9             4862
10            16796
11            58786
12            208012
13            742900
14            2674440
15            9694845


(Expect same result with "Catalan2 15")

VBScript

Function catalan(n)
catalan = factorial(2*n)/(factorial(n+1)*factorial(n))
End Function

Function factorial(n)
If n = 0 Then
Factorial = 1
Else
For i = n To 1 Step -1
If i = n Then
factorial = n
Else
factorial = factorial * i
End If
Next
End If
End Function

'Find the first 15 Catalan numbers.
For j = 1 To 15
WScript.StdOut.Write j & " = " & catalan(j)
WScript.StdOut.WriteLine
Next

Output:
1 = 1
2 = 2
3 = 5
4 = 14
5 = 42
6 = 132
7 = 429
8 = 1430
9 = 4862
10 = 16796
11 = 58786
12 = 208012
13 = 742900
14 = 2674440
15 = 9694845


Visual Basic .NET

Translation of: C#
Module Module1

Function Factorial(n As Double) As Double
If n < 1 Then
Return 1
End If

Dim result = 1.0
For i = 1 To n
result = result * i
Next

Return result
End Function

Function FirstOption(n As Double) As Double
Return Factorial(2 * n) / (Factorial(n + 1) * Factorial(n))
End Function

Function SecondOption(n As Double) As Double
If n = 0 Then
Return 1
End If

Dim sum = 0
For i = 0 To n - 1
sum = sum + SecondOption(i) * SecondOption((n - 1) - i)
Next
Return sum
End Function

Function ThirdOption(n As Double) As Double
If n = 0 Then
Return 1
End If

Return ((2 * (2 * n - 1)) / (n + 1)) * ThirdOption(n - 1)
End Function

Sub Main()
Const MaxCatalanNumber = 15

Dim initial As DateTime
Dim final As DateTime
Dim ts As TimeSpan

initial = DateTime.Now
For i = 0 To MaxCatalanNumber
Console.WriteLine("CatalanNumber({0}:{1})", i, FirstOption(i))
Next
final = DateTime.Now
ts = final - initial
Console.WriteLine("It took {0}.{1} to execute", ts.Seconds, ts.Milliseconds)
Console.WriteLine()

initial = DateTime.Now
For i = 0 To MaxCatalanNumber
Console.WriteLine("CatalanNumber({0}:{1})", i, SecondOption(i))
Next
final = DateTime.Now
ts = final - initial
Console.WriteLine("It took {0}.{1} to execute", ts.Seconds, ts.Milliseconds)
Console.WriteLine()

initial = DateTime.Now
For i = 0 To MaxCatalanNumber
Console.WriteLine("CatalanNumber({0}:{1})", i, ThirdOption(i))
Next
final = DateTime.Now
ts = final - initial
Console.WriteLine("It took {0}.{1} to execute", ts.Seconds, ts.Milliseconds)
End Sub

End Module

Output:
CatalanNumber(0:1)
CatalanNumber(1:1)
CatalanNumber(2:2)
CatalanNumber(3:5)
CatalanNumber(4:14)
CatalanNumber(5:42)
CatalanNumber(6:132)
CatalanNumber(7:429)
CatalanNumber(8:1430)
CatalanNumber(9:4862)
CatalanNumber(10:16796)
CatalanNumber(11:58786)
CatalanNumber(12:208012)
CatalanNumber(13:742900)
CatalanNumber(14:2674440)
CatalanNumber(15:9694845)
It took 0.19 to execute

CatalanNumber(0:1)
CatalanNumber(1:1)
CatalanNumber(2:2)
CatalanNumber(3:5)
CatalanNumber(4:14)
CatalanNumber(5:42)
CatalanNumber(6:132)
CatalanNumber(7:429)
CatalanNumber(8:1430)
CatalanNumber(9:4862)
CatalanNumber(10:16796)
CatalanNumber(11:58786)
CatalanNumber(12:208012)
CatalanNumber(13:742900)
CatalanNumber(14:2674440)
CatalanNumber(15:9694845)
It took 0.831 to execute

CatalanNumber(0:1)
CatalanNumber(1:1)
CatalanNumber(2:2)
CatalanNumber(3:5)
CatalanNumber(4:14)
CatalanNumber(5:42)
CatalanNumber(6:132)
CatalanNumber(7:429)
CatalanNumber(8:1430)
CatalanNumber(9:4862)
CatalanNumber(10:16796)
CatalanNumber(11:58786)
CatalanNumber(12:208012)
CatalanNumber(13:742900)
CatalanNumber(14:2674440)
CatalanNumber(15:9694845)
It took 0.8 to execute

Yabasic

Translation of: FreeBASIC
print "  n   First    Second    Third"
print "  -   -----    ------    -----"
print
for i = 0 to 15
print i using "###", catalan1(i) using "########", catalan2(i) using "########", catalan3(i) using "########"
next i
end

sub factorial(n)
if n = 0  return 1
return n * factorial(n - 1)
end sub

sub catalan1(n)
local proc, i

prod = 1
for i = n + 2 to 2 * n
prod = prod * i
next i
return int(prod / factorial(n))
end sub

sub catalan2(n)
local sum, i

if n = 0  return 1
sum = 0
for i = 0 to n - 1
sum = sum + catalan2(i) * catalan2(n - 1 - i)
next i
return sum
end sub

sub catalan3(n)
if n = 0  return 1
return ((2 * ((2 * n) - 1)) / (n + 1)) * catalan3(n - 1)
end sub
Output:
Same as FreeBASIC entry.

Befunge

0>:.:000p1>\:00g-#v_v
v 2-1*2p00 :+1g00\< $> **00g1+/^v,*84,"="< _^#<*53:+1>#,.#+5< @  Output: 0 = 1 1 = 1 2 = 2 3 = 5 4 = 14 5 = 42 6 = 132 7 = 429 8 = 1430 9 = 4862 10 = 16796 11 = 58786 12 = 208012 13 = 742900 14 = 2674440 15 = 9694845 BQN Cat←{ 0⊸<◶⟨1, (𝕊-⟜1)×(¯2+4×⊢)÷1+⊢⟩ 𝕩 } Fact ← ×´1+↕ Cat1 ← { # direct formula ⌊0.5 + (Fact 2×𝕩) ÷ (Fact 𝕩+1) × Fact 𝕩 } Cat2 ← { # header based recursion 0: 1; (𝕊 𝕩-1)×2×(1-˜2×𝕩)÷𝕩+1 } Cat¨ ↕15 Cat1¨ ↕15 Cat2¨ ↕15  Output: ⟨ 1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440 ⟩ Bracmat ( out$straight
& ( C
=
.   ( F
=   i prod
.   !arg:0&1
|   1:?prod
& 0:?i
&   whl
' ( 1+!i:~>!arg:?i
& !i*!prod:?prod
)
& !prod
)
& F$(2*!arg)*(F$(!arg+1)*F$!arg)^-1 ) & -1:?n & whl ' ( 1+!n:~>15:?n & out$(str$(C !n " = " C$!n))
)
& out$"recursive, with memoization, without fractions" & :?seenCs & ( C = i sum . !arg:0&1 | ( !seenCs:? (!arg.?sum) ? | 0:?sum & -1:?i & whl ' ( 1+!i:<!arg:?i & C$!i*C$(-1+!arg+-1*!i)+!sum:?sum ) & (!arg.!sum) !seenCs:?seenCs ) & !sum ) & -1:?n & whl ' ( 1+!n:~>15:?n & out$(str$(C !n " = " C$!n))
)
& out$"recursive, without memoization, with fractions" & ( C = . !arg:0&1 | 2*(2*!arg+-1)*(!arg+1)^-1*C$(!arg+-1)
)
& -1:?n
&   whl
' ( 1+!n:~>15:?n
& out$(str$(C !n " = " C$!n)) ) & out$"Using taylor expansion of sqrt(1-4X). (See http://bababadalgharaghtakamminarronnkonnbro.blogspot.in/2012/10/algebraic-type-systems-combinatorial.html)"
& out$(1+(1+-1*tay$((1+-4*X)^1/2,X,16))*(2*X)^-1+-1)
& out$); Output: straight C0 = 1 C1 = 1 C2 = 2 C3 = 5 C4 = 14 C5 = 42 C6 = 132 C7 = 429 C8 = 1430 C9 = 4862 C10 = 16796 C11 = 58786 C12 = 208012 C13 = 742900 C14 = 2674440 C15 = 9694845 recursive, with memoization, without fractions C0 = 1 C1 = 1 C2 = 2 C3 = 5 C4 = 14 C5 = 42 C6 = 132 C7 = 429 C8 = 1430 C9 = 4862 C10 = 16796 C11 = 58786 C12 = 208012 C13 = 742900 C14 = 2674440 C15 = 9694845 recursive, without memoization, with fractions C0 = 1 C1 = 1 C2 = 2 C3 = 5 C4 = 14 C5 = 42 C6 = 132 C7 = 429 C8 = 1430 C9 = 4862 C10 = 16796 C11 = 58786 C12 = 208012 C13 = 742900 C14 = 2674440 C15 = 9694845 Using taylor expansion of sqrt(1-4X). (See http://bababadalgharaghtakamminarronnkonnbro.blogspot.in/2012/10/algebraic-type-systems-combinatorial.html) 1 + X + 2*X^2 + 5*X^3 + 14*X^4 + 42*X^5 + 132*X^6 + 429*X^7 + 1430*X^8 + 4862*X^9 + 16796*X^10 + 58786*X^11 + 208012*X^12 + 742900*X^13 + 2674440*X^14 + 9694845*X^15 Brat catalan = { n | true? n == 0 { 1 } { (2 * ( 2 * n - 1) / ( n + 1 )) * catalan(n - 1) } } 0.to 15 { n | p "#{n} - #{catalan n}" } Output: 0 - 1 1 - 1 2 - 2 3 - 5 4 - 14 5 - 42 6 - 132 7 - 429 8 - 1430 9 - 4862 10 - 16796 11 - 58786 12 - 208012 13 - 742900 14 - 2674440 15 - 9694845  C All three methods mentioned in the task: #include <stdio.h> typedef unsigned long long ull; ull binomial(ull m, ull n) { ull r = 1, d = m - n; if (d > n) { n = d; d = m - n; } while (m > n) { r *= m--; while (d > 1 && ! (r%d) ) r /= d--; } return r; } ull catalan1(int n) { return binomial(2 * n, n) / (1 + n); } ull catalan2(int n) { int i; ull r = !n; for (i = 0; i < n; i++) r += catalan2(i) * catalan2(n - 1 - i); return r; } ull catalan3(int n) { return n ? 2 * (2 * n - 1) * catalan3(n - 1) / (1 + n) : 1; } int main(void) { int i; puts("\tdirect\tsumming\tfrac"); for (i = 0; i < 16; i++) { printf("%d\t%llu\t%llu\t%llu\n", i, catalan1(i), catalan2(i), catalan3(i)); } return 0; }  Output:  direct summing frac 0 1 1 1 1 1 1 1 2 2 2 2 3 5 5 5 4 14 14 14 5 42 42 42 6 132 132 132 7 429 429 429 8 1430 1430 1430 9 4862 4862 4862 10 16796 16796 16796 11 58786 58786 58786 12 208012 208012 208012 13 742900 742900 742900 14 2674440 2674440 2674440 15 9694845 9694845 9694845  C# namespace CatalanNumbers { /// <summary> /// Class that holds all options. /// </summary> public class CatalanNumberGenerator { private static double Factorial(double n) { if (n == 0) return 1; return n * Factorial(n - 1); } public double FirstOption(double n) { const double topMultiplier = 2; return Factorial(topMultiplier * n) / (Factorial(n + 1) * Factorial(n)); } public double SecondOption(double n) { if (n == 0) { return 1; } double sum = 0; double i = 0; for (; i <= (n - 1); i++) { sum += SecondOption(i) * SecondOption((n - 1) - i); } return sum; } public double ThirdOption(double n) { if (n == 0) { return 1; } return ((2 * (2 * n - 1)) / (n + 1)) * ThirdOption(n - 1); } } } // Program.cs using System; using System.Configuration; // Main program // Be sure to add the following to the App.config file and add a reference to System.Configuration: // <?xml version="1.0" encoding="utf-8" ?> // <configuration> // <appSettings> // <clear/> // <add key="MaxCatalanNumber" value="50"/> // </appSettings> // </configuration> namespace CatalanNumbers { class Program { static void Main(string[] args) { CatalanNumberGenerator generator = new CatalanNumberGenerator(); int i = 0; DateTime initial; DateTime final; TimeSpan ts; try { initial = DateTime.Now; for (; i <= Convert.ToInt32(ConfigurationManager.AppSettings["MaxCatalanNumber"]); i++) { Console.WriteLine("CatalanNumber({0}):{1}", i, generator.FirstOption(i)); } final = DateTime.Now; ts = final - initial; Console.WriteLine("It took {0}.{1} to execute\n", ts.Seconds, ts.Milliseconds); i = 0; initial = DateTime.Now; for (; i <= Convert.ToInt32(ConfigurationManager.AppSettings["MaxCatalanNumber"]); i++) { Console.WriteLine("CatalanNumber({0}):{1}", i, generator.SecondOption(i)); } final = DateTime.Now; ts = final - initial; Console.WriteLine("It took {0}.{1} to execute\n", ts.Seconds, ts.Milliseconds); i = 0; initial = DateTime.Now; for (; i <= Convert.ToInt32(ConfigurationManager.AppSettings["MaxCatalanNumber"]); i++) { Console.WriteLine("CatalanNumber({0}):{1}", i, generator.ThirdOption(i)); } final = DateTime.Now; ts = final - initial; Console.WriteLine("It took {0}.{1} to execute", ts.Seconds, ts.Milliseconds, ts.TotalMilliseconds); Console.ReadLine(); } catch (Exception ex) { Console.WriteLine("Stopped at index {0}:", i); Console.WriteLine(ex.Message); Console.ReadLine(); } } } }  Output: CatalanNumber(0):1 CatalanNumber(1):1 CatalanNumber(2):2 CatalanNumber(3):5 CatalanNumber(4):14 CatalanNumber(5):42 CatalanNumber(6):132 CatalanNumber(7):429 CatalanNumber(8):1430 CatalanNumber(9):4862 CatalanNumber(10):16796 CatalanNumber(11):58786 CatalanNumber(12):208012 CatalanNumber(13):742900 CatalanNumber(14):2674440 CatalanNumber(15):9694845 It took 0.14 to execute CatalanNumber(0):1 CatalanNumber(1):1 CatalanNumber(2):2 CatalanNumber(3):5 CatalanNumber(4):14 CatalanNumber(5):42 CatalanNumber(6):132 CatalanNumber(7):429 CatalanNumber(8):1430 CatalanNumber(9):4862 CatalanNumber(10):16796 CatalanNumber(11):58786 CatalanNumber(12):208012 CatalanNumber(13):742900 CatalanNumber(14):2674440 CatalanNumber(15):9694845 It took 0.922 to execute CatalanNumber(0):1 CatalanNumber(1):1 CatalanNumber(2):2 CatalanNumber(3):5 CatalanNumber(4):14 CatalanNumber(5):42 CatalanNumber(6):132 CatalanNumber(7):429 CatalanNumber(8):1430 CatalanNumber(9):4862 CatalanNumber(10):16796 CatalanNumber(11):58786 CatalanNumber(12):208012 CatalanNumber(13):742900 CatalanNumber(14):2674440 CatalanNumber(15):9694845 It took 0.3 to execute  C++ 4 Classes We declare 4 classes representing the four different algorithms for calculating Catalan numbers as given in the description of the task. In addition, we declare two supporting classes for the calculation of factorials and binomial coefficients. Because these two are only internal supporting code they are hidden in namespace 'detail'. Overloading the function call operator to execute the calculation is an obvious decision when using C++. (algorithms.h) #if !defined __ALGORITHMS_H__ #define __ALGORITHMS_H__ namespace rosetta { namespace catalanNumbers { namespace detail { class Factorial { public: unsigned long long operator()(unsigned n)const; }; class BinomialCoefficient { public: unsigned long long operator()(unsigned n, unsigned k)const; }; } //namespace detail class CatalanNumbersDirectFactorial { public: CatalanNumbersDirectFactorial(); unsigned long long operator()(unsigned n)const; private: detail::Factorial factorial; }; class CatalanNumbersDirectBinomialCoefficient { public: CatalanNumbersDirectBinomialCoefficient(); unsigned long long operator()(unsigned n)const; private: detail::BinomialCoefficient binomialCoefficient; }; class CatalanNumbersRecursiveSum { public: CatalanNumbersRecursiveSum(); unsigned long long operator()(unsigned n)const; }; class CatalanNumbersRecursiveFraction { public: CatalanNumbersRecursiveFraction(); unsigned long long operator()(unsigned n)const; }; } //namespace catalanNumbers } //namespace rosetta #endif //!defined __ALGORITHMS_H__  Here is the implementation of the algorithms. The c'tor of each class tells us the algorithm which will be used. (algorithms.cpp) #include <iostream> using std::cout; using std::endl; #include <cmath> using std::floor; #include "algorithms.h" using namespace rosetta::catalanNumbers; CatalanNumbersDirectFactorial::CatalanNumbersDirectFactorial() { cout<<"Direct calculation using the factorial"<<endl; } unsigned long long CatalanNumbersDirectFactorial::operator()(unsigned n)const { if(n>1) { unsigned long long nFac = factorial(n); return factorial(2 * n) / ((n + 1) * nFac * nFac); } else { return 1; } } CatalanNumbersDirectBinomialCoefficient::CatalanNumbersDirectBinomialCoefficient() { cout<<"Direct calculation using a binomial coefficient"<<endl; } unsigned long long CatalanNumbersDirectBinomialCoefficient::operator()(unsigned n)const { if(n>1) return double(1) / (n + 1) * binomialCoefficient(2 * n, n); else return 1; } CatalanNumbersRecursiveSum::CatalanNumbersRecursiveSum() { cout<<"Recursive calculation using a sum"<<endl; } unsigned long long CatalanNumbersRecursiveSum::operator()(unsigned n)const { if(n>1) { const unsigned n_ = n - 1; unsigned long long sum = 0; for(unsigned i = 0; i <= n_; i++) sum += operator()(i) * operator()(n_ - i); return sum; } else { return 1; } } CatalanNumbersRecursiveFraction::CatalanNumbersRecursiveFraction() { cout<<"Recursive calculation using a fraction"<<endl; } unsigned long long CatalanNumbersRecursiveFraction::operator()(unsigned n)const { if(n>1) return (double(2 * (2 * n - 1)) / (n + 1)) * operator()(n-1); else return 1; } unsigned long long detail::Factorial::operator()(unsigned n)const { if(n>1) return n * operator()(n-1); else return 1; } unsigned long long detail::BinomialCoefficient::operator()(unsigned n, unsigned k)const { if(k == 0) return 1; if(n == 0) return 0; double product = 1; for(unsigned i = 1; i <= k; i++) product *= (double(n - (k - i)) / i); return (unsigned long long)(floor(product + 0.5)); }  In order to test what we have done, a class Test is created. Using the template parameters N (number of Catalan numbers to be calculated) and A (the kind of algorithm to be used) the compiler will create code for all the test cases we need. What would C++ be without templates ;-) (tester.h) #if !defined __TESTER_H__ #define __TESTER_H__ #include <iostream> namespace rosetta { namespace catalanNumbers { template <int N, typename A> class Test { public: static void Do() { A algorithm; for(int i = 0; i <= N; i++) std::cout<<"C("<<i<<")\t= "<<algorithm(i)<<std::endl; } }; } //namespace catalanNumbers } //namespace rosetta #endif //!defined __TESTER_H__  Finally, we test the four different algorithms. Note that the first one (direct calculation using the factorial) only works up to N = 10 because some intermediate result (namely (2n)! with n = 11) exceeds the boundaries of an unsigned 64 bit integer. (catalanNumbersTest.cpp) #include "algorithms.h" #include "tester.h" using namespace rosetta::catalanNumbers; int main(int argc, char* argv[]) { Test<10, CatalanNumbersDirectFactorial>::Do(); Test<15, CatalanNumbersDirectBinomialCoefficient>::Do(); Test<15, CatalanNumbersRecursiveFraction>::Do(); Test<15, CatalanNumbersRecursiveSum>::Do(); return 0; }  Output: (source code is compiled both by MS Visual C++ 10.0 (WinXP 32 bit) and GNU g++ 4.4.3 (Ubuntu 10.04 64 bit) compilers) Direct calculation using the factorial C(0) = 1 C(1) = 1 C(2) = 2 C(3) = 5 C(4) = 14 C(5) = 42 C(6) = 132 C(7) = 429 C(8) = 1430 C(9) = 4862 C(10) = 16796 Direct calculation using a binomial coefficient C(0) = 1 C(1) = 1 C(2) = 2 C(3) = 5 C(4) = 14 C(5) = 42 C(6) = 132 C(7) = 428 C(8) = 1430 C(9) = 4862 C(10) = 16796 C(11) = 58786 C(12) = 208012 C(13) = 742900 C(14) = 2674440 C(15) = 9694845 Recursive calculation using a fraction C(0) = 1 C(1) = 1 C(2) = 2 C(3) = 5 C(4) = 14 C(5) = 42 C(6) = 132 C(7) = 429 C(8) = 1430 C(9) = 4862 C(10) = 16796 C(11) = 58786 C(12) = 208012 C(13) = 742900 C(14) = 2674440 C(15) = 9694845 Recursive calculation using a sum C(0) = 1 C(1) = 1 C(2) = 2 C(3) = 5 C(4) = 14 C(5) = 42 C(6) = 132 C(7) = 429 C(8) = 1430 C(9) = 4862 C(10) = 16796 C(11) = 58786 C(12) = 208012 C(13) = 742900 C(14) = 2674440 C(15) = 9694845  Clojure (def ! (memoize #(apply * (range 1 (inc %))))) (defn catalan-numbers-direct [] (map #(/ (! (* 2 %)) (* (! (inc %)) (! %))) (range))) (def catalan-numbers-recursive #(->> [1 1] ; [c0 n1] (iterate (fn [[c n]] [(* 2 (dec (* 2 n)) (/ (inc n)) c) (inc n)]) ,) (map first ,))) user> (take 15 (catalan-numbers-direct)) (1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440) user> (take 15 (catalan-numbers-recursive)) (1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440)  CLU catalan = iter (amount: int) yields (int) c: int := 1 for n: int in int$from_to(1, amount) do
yield(c)
c := (4*n-2)*c/(n+1)
end
end catalan

start_up = proc ()
po: stream := stream$primary_output() for n: int in catalan(15) do stream$putl(po, int$unparse(n)) end end start_up Output: 1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440 Common Lisp With all three methods defined. (defun catalan1 (n) ;; factorial. CLISP actually has "!" defined for this (labels ((! (x) (if (zerop x) 1 (* x (! (1- x)))))) (/ (! (* 2 n)) (! (1+ n)) (! n)))) ;; cache (defparameter *catalans* (make-array 5 :fill-pointer 0 :adjustable t :element-type 'integer)) (defun catalan2 (n) (if (zerop n) 1 ;; check cache (if (< n (length *catalans*)) (aref *catalans* n) (loop with c = 0 for i from 0 to (1- n) collect (incf c (* (catalan2 i) (catalan2 (- n 1 i)))) ;; lower values always get calculated first, so ;; vector-push-extend is safe finally (progn (vector-push-extend c *catalans*) (return c)))))) (defun catalan3 (n) (if (zerop n) 1 (/ (* 2 (+ n n -1) (catalan3 (1- n))) (1+ n)))) ;;; test all three methods (loop for f in (list #'catalan1 #'catalan2 #'catalan3) for i from 1 to 3 do (format t "~%Method ~d:~%" i) (dotimes (i 16) (format t "C(~2d) = ~d~%" i (funcall f i))))  Cowgol include "cowgol.coh"; sub catalan(n: uint32): (c: uint32) is c := 1; var i: uint32 := 1; while i <= n loop c := (4*i-2)*c/(i+1); i := i+1; end loop; end sub; var i: uint8 := 0; while i < 15 loop print("catalan("); print_i8(i); print(") = "); print_i32(catalan(i as uint32)); print_nl(); i := i+1; end loop; Output: catalan(0) = 1 catalan(1) = 1 catalan(2) = 2 catalan(3) = 5 catalan(4) = 14 catalan(5) = 42 catalan(6) = 132 catalan(7) = 429 catalan(8) = 1430 catalan(9) = 4862 catalan(10) = 16796 catalan(11) = 58786 catalan(12) = 208012 catalan(13) = 742900 catalan(14) = 2674440 Crystal Translation of: Ruby require "big" require "benchmark" def factorial(n : BigInt) : BigInt (1..n).product(1.to_big_i) end def factorial(n : Int32 | Int64) factorial n.to_big_i end # direct def catalan_direct(n) factorial(2*n) / (factorial(n + 1) * factorial(n)) end # recursive def catalan_rec1(n) return 1 if n == 0 (0...n).reduce(0) do |sum, i| sum + catalan_rec1(i) * catalan_rec1(n - 1 - i) end end def catalan_rec2(n) return 1 if n == 0 2*(2*n - 1) * catalan_rec2(n - 1) / (n + 1) end # performance and results Benchmark.bm do |b| b.report("catalan_direct") { 16.times { |n| catalan_direct(n) } } b.report("catalan_rec1") { 16.times { |n| catalan_rec1(n) } } b.report("catalan_rec2") { 16.times { |n| catalan_rec2(n) } } end puts "\n direct rec1 rec2" 16.times { |n| puts "%2d :%9d%9d%9d" % [n, catalan_direct(n), catalan_rec1(n), catalan_rec2(n)] }  Output: # with --release flag # Using: i7-6700HQ, 3.5GHz user system total real catalan_direct 0.000026 0.000052 0.000078 ( 0.000074) catalan_rec1 0.139766 0.001143 0.140909 ( 0.141418) catalan_rec2 0.000003 0.000000 0.000003 ( 0.000003) direct rec1 rec2 0 : 1 1 1 1 : 1 1 1 2 : 2 2 2 3 : 5 5 5 4 : 14 14 14 5 : 42 42 42 6 : 132 132 132 7 : 429 429 429 8 : 1430 1430 1430 9 : 4862 4862 4862 10 : 16796 16796 16796 11 : 58786 58786 58786 12 : 208012 208012 208012 13 : 742900 742900 742900 14 : 2674440 2674440 2674440 15 : 9694845 9694845 9694845  D import std.stdio, std.algorithm, std.bigint, std.functional, std.range; auto product(R)(R r) { return reduce!q{a * b}(1.BigInt, r); } const cats1 = sequence!((a, n) => iota(n+2, 2*n+1).product / iota(1, n+1).product)(1); BigInt cats2a(in uint n) { alias mcats2a = memoize!cats2a; if (n == 0) return 1.BigInt; return n.iota.map!(i => mcats2a(i) * mcats2a(n - 1 - i)).sum; } const cats2 = sequence!((a, n) => n.cats2a); const cats3 = recurrence!q{ (4*n - 2) * a[n - 1] / (n + 1) }(1.BigInt); void main() { foreach (cats; TypeTuple!(cats1, cats2, cats3)) cats.take(15).writeln; }  Output: [1, 1, 2, 5, 14, 42, 132, 429, 1430, 4862, 16796, 58786, 208012, 742900, 2674440] [1, 1, 2, 5, 14, 42, 132, 429, 1430, 4862, 16796, 58786, 208012, 742900, 2674440] [1, 1, 2, 5, 14, 42, 132, 429, 1430, 4862, 16796, 58786, 208012, 742900, 2674440] Delphi See Pascal. EasyLang func catalan n . if n = 0 return 1 . return 2 * (2 * n - 1) * catalan (n - 1) div (1 + n) . for i = 0 to 14 print catalan i .  EchoLisp  This example is incorrect. Please fix the code and remove this message.Details: series starts 1, 1, 2, ... (lib 'sequences) (lib 'bigint) (lib 'math) ;; function definition (define (C1 n) (/ (factorial (* n 2)) (factorial (1+ n)) (factorial n))) (for ((i [1 .. 16])) (write (C1 i))) → 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440 9694845 ;; using a recursive procedure with memoization (define (C2 n) ;; ( Σ ...)is the same as (sigma ..) (Σ (lambda(i) (* (C2 i) (C2 (- n i 1)))) 0 (1- n))) (remember 'C2 #(1)) ;; first term defined here (for ((i [1 .. 16])) (write (C2 i))) → 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440 9694845 ;; using procrastinators = infinite sequence (define (catalan n acc) (/ (* acc 2 (1- (* 2 n))) (1+ n))) (define C3 (scanl catalan 1 [1 ..])) (take C3 15) → (1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440 9694845) ;; the same, using infix notation (lib 'match) (load 'infix.glisp) (define (catalan n acc) ((2 * acc * ( 2 * n - 1)) / (n + 1))) (define C3 (scanl catalan 1 [1 ..])) (take C3 15) → (1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440 9694845) ;; or (for ((c C3) (i 15)) (write c)) → 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440 9694845  EDSAC order code The Catalan numbers are here computed by the second method, as a sum of products. The program illustrates a difficulty with multiplying integers on the EDSAC, which was designed to work with fixed-point numbers in the range [-1, 1). When we store a 35-bit integer A, we are really storing A*(2^-34). As long as integer arithmetic is confined to addition and subtraction, this scaling can be ignored. But if we multiply two 35-bit integers A and B, the result is really A*B*(2^-68), and needs to be multiplied by 2^34 to get the same scaling as for A and B.  [Calculation of Catalan numbers. EDSAC program, Initial Orders 2.] [Define where to store the list of Catalan numbers.] T 54 K [store address in location 54, so that values are accessed by code letter C (for Catalan)] P 200 F [<------ address here] [Modification of library subroutine P7. Prints signed integer up to 10 digits, right-justified. 54 storage locations; working position 4D. Must be loaded at an even address. Input: Number is at 0D.] T 56 K GKA3FT42@A47@T31@ADE10@T31@A48@T31@SDTDH44#@NDYFLDT4DS43@TF H17@S17@A43@G23@UFS43@T1FV4DAFG50@SFLDUFXFOFFFSFL4FT4DA49@T31@ A1FA43@G20@XFP1024FP610D@524D!FO46@O26@XFO46@SFL8FT4DE39@ [Main routine] T 120 K [load at 120] G K [set @ (theta) to load address] [Variables] [0] P F [index of Catalan number] [Constants] [1] P 7 D [maximum index required] [2] P D [single-word 1] [3] P 2 F [to change addresses by 2] [4] H #C [these 3 are used to manufacture EDSAC orders] [5] T #C [6] V #C [7] K 4096 F [(1) add to change T order into H order (2) teleprinter null] [8] # F [figures shift] [9] ! F [space] [10] @ F [carriage return] [11] & F [line feed] [Enter with acc = 0] [12] O 8 @ [set teleprinter to figures] T 4 D [clear 5F and sandwich bit] A 2 @ [load single-word 1] T 4 F [store as double word at 4D; clear acc] [Here with index in acc, Catalan number in 4D] [16] U @ [store index] L 1 F [times 4 by shifting] A 5 @ [make T order to store Catalan number] U 27 @ [plant in code] A 7 @ [make H order with same address] U 45 @ [plant in code] S 47 @ [make A order with same address] T 34 @ [plant in code] A 6 @ [load V order for start of list] T 46 @ [plant in code] A 4 D [Catalan number from temp store] [27] T #C [store in list (manufactured order)] T D [clear 1F and sandwich bit] A @ [load single-word index] T F [store as double word at 0D] [31] A 31 @ [for return from print subroutine] G 56 F [print index] O 9 @ [followed by space] [34] A #C [load Catalan number (manufactured order)] T D [to 0D for printing] [36] A 36 @ [for return from print subroutine] G 56 F [print Catalan number] O 10 @ [followed by new line] O 11 @ T 4 D [clear partial sum] A @ [load index] S 1 @ [reached the maximum?] E 64 @ [if so, jump to exit] [Inner loop to compute sum of products C{i}*C(n-1}] [44] T F [clear acc] [45] H #C [C{n-i} to mult reg (manufactured order)] [46] V #C [acc := C{i}*C{n-i} (manufactiured order)] [Multiply product by 2^34 (see preamble). The 'L F' order is also exploited above to convert an H order into an A order.] [47] L F [shift acc left by 13 (the maximum available)] L F [shift 13 more] L 64 F [shift 8 more, total 34] A 4 D [add partial sum] T 4 D [update partial sum] A 46 @ [inc i in V order] A 3 @ T 46 @ A 45 @ [dec (n - i) in H order] S 3 @ U 45 @ S 4 @ [is (n - i) now negative?] E 44 @ [if not, loop back] [Here with latest Catalan number in temp store 4D] T F [clear acc] A @ [load index] A 2 @ [add 1] E 16 @ [back to start of outer loop] [64] O 7 @ [exit; print null to flush teleprinter buffer] Z F [stop] E 12 Z [define entry point] P F [acc = 0 on entry] Output:  0 1 1 1 2 2 3 5 4 14 5 42 6 132 7 429 8 1430 9 4862 10 16796 11 58786 12 208012 13 742900 14 2674440 15 9694845  Eiffel class APPLICATION create make feature {NONE} make do across 0 |..| 14 as c loop io.put_double (nth_catalan_number (c.item)) io.new_line end end nth_catalan_number (n: INTEGER): DOUBLE --'n'th number in the sequence of Catalan numbers. require n_not_negative: n >= 0 local s, t: DOUBLE do if n = 0 then Result := 1.0 else t := 4 * n.to_double - 2 s := n.to_double + 1 Result := t / s * nth_catalan_number (n - 1) end end end  Output: 1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440  Elixir Translation of: Erlang defmodule Catalan do def cat(n), do: div( factorial(2*n), factorial(n+1) * factorial(n) ) defp factorial(n), do: fac1(n,1) defp fac1(0, acc), do: acc defp fac1(n, acc), do: fac1(n-1, n*acc) def cat_r1(0), do: 1 def cat_r1(n), do: Enum.sum(for i <- 0..n-1, do: cat_r1(i) * cat_r1(n-1-i)) def cat_r2(0), do: 1 def cat_r2(n), do: div(cat_r2(n-1) * 2 * (2*n - 1), n + 1) def test do range = 0..14 :io.format "Directly:~n~p~n", [(for n <- range, do: cat(n))] :io.format "1st recusive method:~n~p~n", [(for n <- range, do: cat_r1(n))] :io.format "2nd recusive method:~n~p~n", [(for n <- range, do: cat_r2(n))] end end Catalan.test  Output: Directly: [1,1,2,5,14,42,132,429,1430,4862,16796,58786,208012,742900,2674440] 1st recusive method: [1,1,2,5,14,42,132,429,1430,4862,16796,58786,208012,742900,2674440] 2nd recusive method: [1,1,2,5,14,42,132,429,1430,4862,16796,58786,208012,742900,2674440]  Erlang -module(catalan). -export([test/0]). cat(N) -> factorial(2 * N) div (factorial(N+1) * factorial(N)). factorial(N) -> fac1(N,1). fac1(0,Acc) -> Acc; fac1(N,Acc) -> fac1(N-1, N * Acc). cat_r1(0) -> 1; cat_r1(N) -> lists:sum([cat_r1(I)*cat_r1(N-1-I) || I <- lists:seq(0,N-1)]). cat_r2(0) -> 1; cat_r2(N) -> cat_r2(N - 1) * (2 * ((2 * N) - 1)) div (N + 1). test() -> TestList = lists:seq(0,14), io:format("Directly:\n~p\n",[[cat(N) || N <- TestList]]), io:format("1st recusive method:\n~p\n",[[cat_r1(N) || N <- TestList]]), io:format("2nd recusive method:\n~p\n",[[cat_r2(N) || N <- TestList]]).  Output: Directly: [1,1,2,5,14,42,132,429,1430,4862,16796,58786,208012,742900,2674440] 1st recusive method: [1,1,2,5,14,42,132,429,1430,4862,16796,58786,208012,742900,2674440] 2nd recusive method: [1,1,2,5,14,42,132,429,1430,4862,16796,58786,208012,742900,2674440]  ERRE PROGRAM CATALAN PROCEDURE CATALAN(N->RES) RES=1 FOR I=1 TO N DO RES=RES*2*(2*I-1)/(I+1) END FOR END PROCEDURE BEGIN FOR N=0 TO 15 DO CATALAN(N->RES) PRINT(N;"=";RES) END FOR END PROGRAM  Output:  0 = 1 1 = 1 2 = 2 3 = 5 4 = 14 5 = 42 6 = 132 7 = 429 8 = 1430 9 = 4862 10 = 16796 11 = 58786 12 = 208012 13 = 742900 14 = 2674440 15 = 9694845  Euphoria --Catalan number task from Rosetta Code wiki --User:Lnettnay --function from factorial task function factorial(integer n) atom f = 1 while n > 1 do f *= n n -= 1 end while return f end function function catalan(integer n) atom numerator = factorial(2 * n) atom denominator = factorial(n+1)*factorial(n) return numerator/denominator end function for i = 0 to 15 do ? catalan(i) end for Output: 1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440 9694845  F# Seq.unfold(fun (c,n) -> let cc = 2*(2*n-1)*c/(n+1) in Some(c,(cc,n+1))) (1,1) |> Seq.take 15 |> Seq.iter (printf "%i, ")  Output: 1, 1, 2, 5, 14, 42, 132, 429, 1430, 4862, 16796, 58786, 208012, 742900, 2674440,  Factor The first method: USING: kernel math math.combinatorics prettyprint ; : catalan ( n -- n ) [ 1 + recip ] [ 2 * ] [ nCk * ] tri ; 15 [ catalan . ] each-integer  Output: 1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440  The last method, memoized by using arrays. USING: kernel math prettyprint sequences ; : next ( seq -- newseq ) [ ] [ last ] [ length ] tri [ 2 * 1 - 2 * ] [ 1 + ] bi / * suffix ; : Catalan ( n -- seq ) V{ 1 } swap 1 - [ next ] times ; 15 Catalan .  Output: Similar to above. Fantom  This example is incorrect. Please fix the code and remove this message.Details: series starts 1, 1, 2, ... class Main { static Int factorial (Int n) { Int res := 1 if (n>1) (2..n).each |i| { res *= i } return res } static Int catalanA (Int n) { return factorial(2*n)/(factorial(n+1) * factorial(n)) } static Int catalanB (Int n) { if (n == 0) { return 1 } else { sum := 0 n.times |i| { sum += catalanB(i) * catalanB(n-1-i) } return sum } } static Int catalanC (Int n) { if (n == 0) { return 1 } else { return catalanC(n-1)*2*(2*n-1)/(n+1) } } public static Void main () { (1..15).each |n| { echo (n.toStr.padl(4) + catalanA(n).toStr.padl(10) + catalanB(n).toStr.padl(10) + catalanC(n).toStr.padl(10)) } } } 22! exceeds the range of Fantom's Int class, so the first technique fails afer n=10  1 1 1 1 2 2 2 2 3 5 5 5 4 14 14 14 5 42 42 42 6 132 132 132 7 429 429 429 8 1430 1430 1430 9 4862 4862 4862 10 16796 16796 16796 11 -65 58786 58786 12 -2 208012 208012 13 0 742900 742900 14 97 2674440 2674440 15 -2 9694845 9694845  Fermat Func Catalan(n)=(2*n)!/((n+1)!*n!).; for i=1 to 15 do !Catalan(i);!' ' od; Output:  1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440 9694845  Forth : catalan ( n -- ) 1 swap 1+ 1 do dup cr . i 2* 1- 2* i 1+ */ loop drop ;  Fortran Works with: Fortran version 90 and later program main !======================================================================================= implicit none !=== Local data integer :: n !=== External procedures double precision, external :: catalan_numbers !=== Execution ========================================================================= write(*,'(1x,a)')'===============' write(*,'(5x,a,6x,a)')'n','c(n)' write(*,'(1x,a)')'---------------' do n = 0, 14 write(*,'(1x,i5,i10)') n, int(catalan_numbers(n)) enddo write(*,'(1x,a)')'===============' !======================================================================================= end program main !BL !BL !BL double precision recursive function catalan_numbers(n) result(value) !======================================================================================= implicit none !=== Input, ouput data integer, intent(in) :: n !=== Execution ========================================================================= if ( n .eq. 0 ) then value = 1 else value = ( 2.0d0 * dfloat(2 * n - 1) / dfloat( n + 1 ) ) * catalan_numbers(n-1) endif !======================================================================================= end function catalan_numbers  Output:  =============== n c(n) --------------- 0 1 1 1 2 2 3 5 4 14 5 42 6 132 7 429 8 1430 9 4862 10 16796 11 58786 12 208012 13 742900 14 2674440 ===============  Frink Frink includes efficient algorithms for calculating arbitrarily-large binomial coefficients and automatically caches factorials. catalan[n] := binomial[2n,n]/(n+1) for n = 0 to 15 println[catalan[n]] FunL import integers.choose import util.TextTable def catalan( n ) = choose( 2n, n )/(n + 1) catalan2( n ) = product( (n + k)/k | k <- 2..n ) catalan3( 0 ) = 1 catalan3( n ) = 2*(2n - 1)/(n + 1)*catalan3( n - 1 ) t = TextTable() t.header( 'n', 'definition', 'product', 'recursive' ) t.line() for i <- 1..4 t.rightAlignment( i ) for i <- 0..15 t.row( i, catalan(i), catalan2(i), catalan3(i) ) println( t ) Output: +----+------------+---------+-----------+ | n | definition | product | recursive | +----+------------+---------+-----------+ | 0 | 1 | 1 | 1 | | 1 | 1 | 1 | 1 | | 2 | 2 | 2 | 2 | | 3 | 5 | 5 | 5 | | 4 | 14 | 14 | 14 | | 5 | 42 | 42 | 42 | | 6 | 132 | 132 | 132 | | 7 | 429 | 429 | 429 | | 8 | 1430 | 1430 | 1430 | | 9 | 4862 | 4862 | 4862 | | 10 | 16796 | 16796 | 16796 | | 11 | 58786 | 58786 | 58786 | | 12 | 208012 | 208012 | 208012 | | 13 | 742900 | 742900 | 742900 | | 14 | 2674440 | 2674440 | 2674440 | | 15 | 9694845 | 9694845 | 9694845 | +----+------------+---------+-----------+  Fōrmulæ Fōrmulæ programs are not textual, visualization/edition of programs is done showing/manipulating structures but not text. Moreover, there can be multiple visual representations of the same program. Even though it is possible to have textual representation —i.e. XML, JSON— they are intended for storage and transfer purposes more than visualization and edition. Programs in Fōrmulæ are created/edited online in its website. In this page you can see and run the program(s) related to this task and their results. You can also change either the programs or the parameters they are called with, for experimentation, but remember that these programs were created with the main purpose of showing a clear solution of the task, and they generally lack any kind of validation. Solution Direct definition Direct definition (alternative) The expression ${\displaystyle {\frac {(2n)!}{(n+1)!\,n!}}}$ turns out to be equals to ${\displaystyle \prod _{k=2}^{n}{\frac {n+k}{k}}}$ (same result) No directly defined Recursive definitions are easy to write, but extremely inefficient (specially the first one). Because a list is intended to be get, the list of previous values can be used as a form of memoization, avoiding recursion. The next function make use of the "second" form of recursive definition (without recursion): (same result) GAP Catalan1 := n -> Binomial(2*n, n) - Binomial(2*n, n - 1); Catalan2 := n -> Binomial(2*n, n)/(n + 1); Catalan3 := function(n) local k, c; c := 1; k := 0; while k < n do k := k + 1; c := 2*(2*k - 1)*c/(k + 1); od; return c; end; Catalan4_memo := [1]; Catalan4 := function(n) if not IsBound(Catalan4_memo[n + 1]) then Catalan4_memo[n + 1] := Sum([0 .. n - 1], i -> Catalan4(i)*Catalan4(n - 1 - i)); fi; return Catalan4_memo[n + 1]; end; # The first fifteen: 0 to 14 ! List([0 .. 14], Catalan1); List([0 .. 14], Catalan2); List([0 .. 14], Catalan3); List([0 .. 14], Catalan4); # Same output for all four: # [ 1, 1, 2, 5, 14, 42, 132, 429, 1430, 4862, 16796, 58786, 208012, 742900, 2674440 ]  Go Direct: package main import ( "fmt" "math/big" ) func main() { var b, c big.Int for n := int64(0); n < 15; n++ { fmt.Println(c.Div(b.Binomial(n*2, n), c.SetInt64(n+1))) } }  Output: 1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440  Recursive (alternative): package main import ( "fmt" "math/big" ) func c(n int64) *big.Int { if n == 0 { return big.NewInt(1) } else { var t1, t2, t3, t4, t5, t6 big.Int t1.Mul(big.NewInt(2), big.NewInt(n)) t2.Sub(&t1, big.NewInt(1)) t3.Mul(big.NewInt(2), &t2) t4.Add(big.NewInt(n), big.NewInt(1)) t5.Mul(&t3, c(n-1)) t6.Div(&t5, &t4) return &t6 } } func main() { for n := int64(1); n < 16; n++ { fmt.Println(c(n)) } }  Output: 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440 9694845  Groovy class Catalan { public static void main(String[] args) { BigInteger N = 15; BigInteger k,n,num,den; BigInteger catalan; print(1); for(n=2;n<=N;n++) { num = 1; den = 1; for(k=2;k<=n;k++) { num = num*(n+k); den = den*k; catalan = num/den; } println(catalan); } } }  Output: 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440 9694845  Harbour PROCEDURE Main() LOCAL i FOR i := 0 to 15 ? PadL( i, 2 ) + ": " + hb_StrFormat("%d", Catalan( i )) NEXT RETURN STATIC FUNCTION Catalan( n ) LOCAL i, nCatalan := 1 FOR i := 1 TO n nCatalan := nCatalan * 2 * (2 * i - 1) / (i + 1) NEXT RETURN nCatalan  Output: 0: 1 1: 1 2: 2 3: 5 4: 14 5: 42 6: 132 7: 429 8: 1430 9: 4862 0: 16796 1: 58786 2: 208012 3: 742900 4: 2674440 5: 9694845  Haskell -- Three infinite lists, corresponding to the three -- definitions in the problem statement. cats1 :: [Integer] cats1 = (div . product . (enumFromTo . (2 +) <*> (2 *))) <*> (product . enumFromTo 1) <$> [0 ..]

cats2 :: [Integer]
cats2 =
1 :
fmap
(\n -> sum (zipWith (*) (reverse (take n cats2)) cats2))
[1 ..]

cats3 :: [Integer]
cats3 =
scanl
(\c n -> c * 2 * (2 * n - 1) div succ n)
1
[1 ..]

main :: IO ()
main = mapM_ (print . take 15) [cats1, cats2, cats3]

Output:
[1,1,2,5,14,42,132,429,1430,4862,16796,58786,208012,742900,2674440]
[1,1,2,5,14,42,132,429,1430,4862,16796,58786,208012,742900,2674440]
[1,1,2,5,14,42,132,429,1430,4862,16796,58786,208012,742900,2674440]

Icon and Unicon

procedure main()
every writes(catalan(0 to 14)," ")
end

procedure catalan(n) # return catalan(n) or fail
static M
initial M := table()
n=0 & return 1

if n > 0 then
return (n = 1) | \M[n] | ( M[n] := (2*(2*n-1)*catalan(n-1))/(n+1))
end

Output:
1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440

J

   ((! +:) % >:) i.15x
1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440


Java

Replace double inexact computations with BigInteger implementation.

import java.math.BigInteger;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class CatlanNumbers {

public static void main(String[] args) {
Catlan f1 = new Catlan1();
Catlan f2 = new Catlan2();
Catlan f3 = new Catlan3();
System.out.printf("           Formula 1     Formula 2     Formula 3%n");
for ( int n = 0 ; n <= 15 ; n++ ) {
System.out.printf("C(%2d) = %,12d  %,12d  %,12d%n", n, f1.catlin(n), f2.catlin(n), f3.catlin(n));
}
}

private static interface Catlan {
public BigInteger catlin(long n);
}

private static class Catlan1 implements Catlan {

//  C(n) = (2n)! / (n+1)!n!
@Override
public BigInteger catlin(long n) {
List<Long> numerator = new ArrayList<>();
for ( long k = n+2 ; k <= 2*n ; k++ ) {
}

List<Long> denominator = new ArrayList<>();
for ( long k = 2 ; k <= n ; k++ ) {
}

for ( int i = numerator.size()-1 ; i >= 0  ; i-- ) {
for ( int j = denominator.size()-1 ; j >= 0  ; j-- ) {
if ( denominator.get(j) == 1 ) {
continue;
}
if ( numerator.get(i) % denominator.get(j) == 0 ) {
long val = numerator.get(i) / denominator.get(j);
numerator.set(i, val);
denominator.remove(denominator.get(j));
if ( val == 1 ) {
break;
}
}
}
}

BigInteger catlin = BigInteger.ONE;
for ( int i = 0 ; i < numerator.size() ; i++ ) {
catlin = catlin.multiply(BigInteger.valueOf(numerator.get(i)));
}
for ( int i = 0 ; i < denominator.size() ; i++ ) {
catlin = catlin.divide(BigInteger.valueOf(denominator.get(i)));
}
return catlin;
}
}

private static class Catlan2 implements Catlan {

private static Map<Long,BigInteger> CACHE = new HashMap<>();
static {
CACHE.put(0L, BigInteger.ONE);
}

//  C(0) = 1, C(n+1) = sum(i=0..n,C(i)*C(n-i))
@Override
public BigInteger catlin(long n) {
if ( CACHE.containsKey(n) ) {
return CACHE.get(n);
}
BigInteger catlin = BigInteger.ZERO;
n--;
for ( int i = 0 ; i <= n ; i++ ) {
//System.out.println("n = " + n + ", i = " + i + ", n-i = " + (n-i));
}
CACHE.put(n+1, catlin);
return catlin;
}
}

private static class Catlan3 implements Catlan {

private static Map<Long,BigInteger> CACHE = new HashMap<>();
static {
CACHE.put(0L, BigInteger.ONE);
}

//  C(0) = 1, C(n+1) = 2*(2n-1)*C(n-1)/(n+1)
@Override
public BigInteger catlin(long n) {
if ( CACHE.containsKey(n) ) {
return CACHE.get(n);
}
BigInteger catlin = BigInteger.valueOf(2).multiply(BigInteger.valueOf(2*n-1)).multiply(catlin(n-1)).divide(BigInteger.valueOf(n+1));
CACHE.put(n, catlin);
return catlin;
}
}

}

Output:
           Formula 1     Formula 2     Formula 3
C( 0) =            1             1             1
C( 1) =            1             1             1
C( 2) =            2             2             2
C( 3) =            5             5             5
C( 4) =           14            14            14
C( 5) =           42            42            42
C( 6) =          132           132           132
C( 7) =          429           429           429
C( 8) =        1,430         1,430         1,430
C( 9) =        4,862         4,862         4,862
C(10) =       16,796        16,796        16,796
C(11) =       58,786        58,786        58,786
C(12) =      208,012       208,012       208,012
C(13) =      742,900       742,900       742,900
C(14) =    2,674,440     2,674,440     2,674,440
C(15) =    9,694,845     9,694,845     9,694,845


JavaScript

Procedural

<html><head><title>Catalan</title></head>
<body><pre id='x'></pre><script type="application/javascript">
function disp(x) {
var e = document.createTextNode(x + '\n');
document.getElementById('x').appendChild(e);
}

var fc = [], c2 = [], c3 = [];
function fact(n) { return fc[n] ? fc[n] : fc[n] = (n ? n * fact(n - 1) : 1); }
function cata1(n) { return Math.floor(fact(2 * n) / fact(n + 1) / fact(n) + .5); }
function cata2(n) {
if (n == 0) return 1;
if (!c2[n]) {
var s = 0;
for (var i = 0; i < n; i++) s += cata2(i) * cata2(n - i - 1);
c2[n] = s;
}
return c2[n];
}
function cata3(n) {
if (n == 0) return 1;
return c3[n] ? c3[n] : c3[n] = (4 * n - 2) * cata3(n - 1) / (n + 1);
}

disp("       meth1   meth2   meth3");
for (var i = 0; i <= 15; i++)
disp(i + '\t' + cata1(i) + '\t' + cata2(i) + '\t' + cata3(i));

</script></body></html>

Output:
       meth1   meth2   meth3
0	1	1	1
1	1	1	1
2	2	2	2
3	5	5	5
4	14	14	14
5	42	42	42
6	132	132	132
7	429	429	429
8	1430	1430	1430
9	4862	4862	4862
10	16796	16796	16796
11	58786	58786	58786
12	208012	208012	208012
13	742900	742900	742900
14	2674440	2674440	2674440
15	9694845	9694845	9694845

Functional

Defining an infinite list:

(() => {
"use strict";

// ----------------- CATALAN NUMBERS -----------------

// catalansDefinitionThree :: [Int]
const catalansDefinitionThree = () =>
// An infinite sequence of Catalan numbers.
scanlGen(
c => n => Math.floor(
(2 * c * pred(2 * n)) / succ(n)
)
)(1)(
enumFrom(1)
);

// ---------------------- TEST -----------------------
// main :: IO ()
const main = () =>
take(15)(
catalansDefinitionThree()
);

// --------------------- GENERIC ---------------------

// enumFrom :: Enum a => a -> [a]
const enumFrom = function* (n) {
// An infinite sequence of integers,
// starting with n.
let v = n;

while (true) {
yield v;
v = 1 + v;
}
};

// pred :: Int -> Int
const pred = x =>
x - 1;

// scanlGen :: (b -> a -> b) -> b -> Gen [a] -> [b]
const scanlGen = f =>
// The series of interim values arising
// from a catamorphism over an infinite list.
startValue => function* (gen) {
let
a = startValue,
x = gen.next();

yield a;
while (!x.done) {
a = f(a)(x.value);
yield a;
x = gen.next();
}
};

// succ :: Int -> Int
const succ = x =>
1 + x;

// take :: Int -> [a] -> [a]
// take :: Int -> String -> String
const take = n =>
// The first n elements of a list,
// string of characters, or stream.
xs => Array.from({
length: n
}, () => {
const x = xs.next();

return x.done ? [] : [x.value];
}).flat();

// MAIN ---
return JSON.stringify(main(), null, 2);
})();

Output:
[
1,
1,
2,
5,
14,
42,
132,
429,
1430,
4862,
16796,
58786,
208012,
742900,
2674440
]

jq

Works with: jq version 1.4

The recursive formula for C(n) in terms of C(n-1) lends itself directly to efficient implementations in jq so in this section, that formula is used (a) to define a function for computing a single Catalan number; (b) to define a function for generating a sequence of Catalan numbers; and (c) to write a single expression for generating a sequence of Catalan numbers using jq's builtin "recurse/1" filter.

Compute a single Catalan number

def catalan:
if . == 0 then 1
elif . < 0 then error("catalan is not defined on \(.)")
else (2 * (2*. - 1) * ((. - 1) | catalan)) / (. + 1)
end;

Example 1

(range(0; 16), 100) as $i |$i | catalan | [$i, .] Output: $ jq -M -n -c -f Catalan_numbers.jq
[0,1]
[1,1]
[2,2]
[3,5]
[4,14]
[5,42]
[6,132]
[7,429]
[8,1430]
[9,4862]
[10,16796]
[11,58786]
[12,208012]
[13,742900]
[14,2674440]
[15,9694845]
[100,8.96519947090131e+56]


Generate a sequence of Catalan numbers

def catalan_series(max):
def _catalan: # state: [n, catalan(n)]
if .[0] > max then empty
else .,
((.[0] + 1) as $n | .[1] as$cp
| [$n, (2 * (2*$n - 1) * $cp) / ($n + 1) ] | _catalan)
end;
[0,1] | _catalan;

Example 2:

catalan_series(15)
Output:
As above for 0 to 15.


An expression to generate Catalan numbers

  [0,1]
| recurse( if .[0] == 15 then empty
else .[1] as $c | (.[0] + 1) | [ ., (2 * (2*. - 1) *$c) / (. + 1) ]
end )
Output:
As above for 0 to 15.


Julia

Works with: Julia version 0.6
catalannum(n::Integer) = binomial(2n, n) ÷ (n + 1)

@show catalannum.(1:15)
@show catalannum(big(100))

Output:
catalannum.(1:15) = [1, 2, 5, 14, 42, 132, 429, 1430, 4862, 16796, 58786, 208012, 742900, 2674440, 9694845]
catalannum(big(100)) = 896519947090131496687170070074100632420837521538745909320

(In the second example, we have used arbitrary-precision integers to avoid overflow for large Catalan numbers.)

K

  catalan: {_{*/(x-i)%1+i:!y-1}[2*x;x+1]%x+1}
catalan'!:15
1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440


Kotlin

Works with: Java version 1.7.0
Works with: Kotlin version 1.1.4
abstract class Catalan {
abstract operator fun invoke(n: Int) : Double

protected val m = mutableMapOf(0 to 1.0)
}

object CatalanI : Catalan() {
override fun invoke(n: Int): Double {
if (n !in m)
m[n] = Math.round(fact(2 * n) / (fact(n + 1) * fact(n))).toDouble()
return m[n]!!
}

private fun fact(n: Int): Double {
if (n in facts)
return facts[n]!!
val f = n * fact(n -1)
facts[n] = f
return f
}

private val facts = mutableMapOf(0 to 1.0, 1 to 1.0, 2 to 2.0)
}

object CatalanR1 : Catalan() {
override fun invoke(n: Int): Double {
if (n in m)
return m[n]!!

var sum = 0.0
for (i in 0..n - 1)
sum += invoke(i) * invoke(n - 1 - i)
sum = Math.round(sum).toDouble()
m[n] = sum
return sum
}
}

object CatalanR2 : Catalan() {
override fun invoke(n: Int): Double {
if (n !in m)
m[n] = Math.round(2.0 * (2 * (n - 1) + 1) / (n + 1) * invoke(n - 1)).toDouble()
return m[n]!!
}
}

fun main(args: Array<String>) {
val c = arrayOf(CatalanI, CatalanR1, CatalanR2)
for(i in 0..15) {
c.forEach { print("%9d".format(it(i).toLong())) }
println()
}
}

Output:
        1        1        1
1        1        1
2        2        2
5        5        5
14       14       14
42       42       42
132      132      132
429      429      429
1430     1430     1430
4862     4862     4862
16796    16796    16796
58786    58786    58786
208012   208012   208012
742900   742900   742900
2674440  2674440  2674440
9694845  9694845  9694845

Lambdatalk

Translation of: Javascript

1) catalan1

{def catalan1
{def fac {lambda {:n} {* {S.serie 1 :n}}}}
{lambda {:n}
{floor {+ {/ {fac {* 2 :n}} {fac {+ :n 1}} {fac :n}} 0.5}}}}
-> catalan1

{S.map catalan1 {S.serie 1 15}}
->  1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440 9694845


2) catalan2

{def catalan2
{def catalan2.sum
{lambda {:n :a :s :i}
{if {= :i :n}
then {A.set! :n :s :a}
else {catalan2.sum :n
:a
{+ :s {* {catalan2.loop :i :a}
{catalan2.loop {- :n :i 1} :a}}}
{+ :i 1}} }}}
{def catalan2.loop
{lambda {:n :a}
{if {= :n 0}
then 1
else {if {W.equal? {A.get :n :a} undefined}
then {A.get :n {catalan2.sum :n :a 0 0}}
else {A.get :n :a} }}}}
{lambda {:n}
{catalan2.loop :n {A.new}} }}
-> catalan2

{S.map catalan2 {S.serie 0 15}}
-> 1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440 9694845


3) catalan3

{def catalan3
{def catalan3.loop
{lambda {:n :a}
{if {= :n 0}
then 1
else {if {W.equal? {A.get :n :a} undefined}
then {A.get :n
{A.set! :n
{/ {* {- {* 4 :n} 2}
{catalan3.loop {- :n 1} :a}}
{+ :n 1}}
:a}}
else {A.get :n :a}
}}}}
{lambda {:n}
{catalan3.loop :n {A.new}}}}
-> catalan3

{S.map catalan3 {S.serie 0 15}}
-> 1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440 9694845


4) Alternative for a vertical diplay

{style
td { text-align:right;
font-family:monospace;
}
}

{table
{tr {td} {td cat1} {td cat2} {td cat3}}
{S.map {lambda {:i} {tr {td :i}
{td {catalan1 :i}}
{td {catalan2 :i}}
{td {catalan3 :i}}}}
{S.serie 0 15}}
}

cat1    cat2    cat3
0 	      1 	  1 	  1
1 	      1 	  1 	  1
2 	      2 	  2 	  2
3 	      5 	  5 	  5
4 	     14 	 14 	 14
5 	     42 	 42 	 42
6 	    132 	132 	132
7 	    429 	429 	429
8 	   1430    1430    1430
9 	   4862    4862    4862
10 	  16796   16796   16796
11 	  58786   58786   58786
12 	 208012  208012  208012
13 	 742900  742900  742900
14 	2674440 2674440 2674440
15 	9694845 9694845 9694845


langur

Translation of: Perl
val factorial = fn x:if(x < 2: 1; x * self(x - 1))

val catalan = fn n:factorial(2 * n) / factorial(n+1) / factorial(n)

for i in 0..15 {
writeln "{{i:2}}: {{catalan(i):10}}"
}

writeln "10000: ", catalan(10000)
Output:
 0:          1
1:          1
2:          2
3:          5
4:         14
5:         42
6:        132
7:        429
8:       1430
9:       4862
10:      16796
11:      58786
12:     208012
13:     742900
14:    2674440
15:    9694845
10000: 224537812493385215633593584257360578701103586219365887773293713835854436588700534490998102719114320210209905393799589701149327326500953702713977513001838761306936534407802585494454599941773729984591764542782202886796997833276495496514760245912220654267091568311812071300891219894022165175451441066691435091975969499731921675488934120638046514134965974069039677192984714638704528752769863567952620334847707274529741976558104236293861846622622783294667505268651205024766408784881872997404042356319626323351089169906635603513309014645157443570842822082866699012415455339518777770781742052837799476906230350785959040487158118992753484022865373274100095762968510625236915280143408460651206678398725681703811505423791566261735329550627967717189932855983913468867794806585863794483869239933179341394259456515091026456652770409848702116046445406995085092488210998732255656992243441519938747425554228724734242623566663631968254490897214106655375215196762710825001305055093871863518797311135688370964194817463890187212845332422257193414201244344808864449873736345425670715824582633802476282521798739438044652622163657359012681653473214512797365047989922327391063907061792126264420963262176161781711086630089636828211837643128677915076724947168653050318426339007489738275045346257959685376480042860870398232333705506506342394485443047987642390287346746539674780326188825579548593281319807827279403944008553690033855132088140116099772393778770685018936338194366302053586633406848404622048675525765095697363909787189635178694239275237185046710057476484117945279786897787624602379494797322427251542758312638233073625857897083435831841717971137851874666094337671443717108457737153283641719103639784923520519013700030680553564442331411313831920775983175313709250333784211385811480015293165463406576311626295629412110652218717603537723650144357966952842696678735624157616428716812764985074925414219421312810089785108621126934245959900367104035334200067714905754827856122801987429837706493130435832752072139392743006620396370486473952500144779413596417260472218266529167783118015414918168260722824885550181735638670588682513610805160133611349864194033776132438535863120087679096358696928233598996870302136347936567444208209125300149683552369341937471817860835774359234009557030148123353114950735217736514617017504851011193104728986836180908987352236659629183725016607437110422583156042941955830763092095074443334625318588569114114087985404048889671202396824806275701581378689568449507132793603852731445602923990458926101180821029108808623323378547869169352237448925371763574346501610378415722137519019474474794069155118626291447578558908522430436148987521551911541787974276591708584289036595642180860178815462862735993859177180582760389253540408842580225467216988321950591728369194164290645992782274919561096308372635908842325870580231011459216934235078490764707633348336131667313582584404397290232519769625777374165187949140092779343812345117947306771376053099536367169631889642304360871187460737580808157222861127968703067542270175460553478533349238111434409526724363429611803844595968793121871649699680963646793415774160274520010905236593324062464542927011227158945796188186430711399250096518886617184049325827319276468018789191520522185358895653192882843061349706085770767046601045697944646638311930027354235643643713545212361580694059553720806659066661496416423676930095857438882302891350789287291844752601744462789158506243012088536936184422120232369244564444689340142897415432231452353338115944183447986470689449043710051589958391273681116292415738776171575775695905846247205522469202801517417551374761549677412720803623129527503286287755308576386461385928958587649159872019202866614901547860974883963007792442796064165417207167072370586790722366932349325253877744621251386864069101337572557790214048760202008337611577675840153696735860276810033694744314488435390547908483357054897387317002405793108554524629034558098886977538473481750772616164313845337139245688079995996839933620829828339492800825536599964878893947278408890351634126931068657027524005795713514365098086505030570362785115155293306343520969872400876180105031975302255898787642403303027682634969586730202117121076117629457710028105378124677420093990476071697970354661002217702623344454780740808459286778553016318604430682610618871098652904537323336381304469735192868285840882036271136058499391069436145426450229039329475974178236465920534171895204155964515055983303017823692138977622016292722019365841360360274557488926673754175222061483328914099598663902320310143583379354121664996173733086613692927391384486261610892314450463841637667054196985332620403539011932606618414419229492637564924726411270720189611019154677281846409387514072618176832310721327819277699943226895919915049652045449281057471199978267843961724883768772155477073354744908923995448752333726740642292872107500458349718026322755698226793850983280706045951407323891263270928264657562125955511946782954645656015480418543664557515041692091317941000997342935512311493290722434384401250133402934163457264794261787386862382738330195237770190998115114193014769006071380834085352290585937952429981509893303796306071520571655936820282768086579891336876000368502562579738337809071051261343359121744773055264455701014137255399929760233753812017596045145926791136761130783810840502248142803073720015451941006030172192834375431286154255159659778817089767964922549014569972777126726537787896968876337799235679125368824867754881036161730805613471278633981478858113141202728303435218970292775366288829203013873713349923690394124920402725698544786016048685431525811047414746045227535216327530901827040588505255466803793791888002231571686068617764292584075135236237044383334893874602177596602979234717936820827427229615827657960492946059695301906791494260652411424538532836730097985187522379068364429583532675896349363295120431429006688249818006722311568902288350452581968418068616818268667067741994472455501649753611708445979082338902214467454627107888156489438584617793175431865532382711812960546611287516640


Logo

to factorial :n
output ifelse [less? :n 1] 1 [product :n factorial difference :n 1]
end
to choose :n :r
output quotient factorial :n product factorial :r factorial difference :n :r
end
to catalan :n
output product (quotient sum :n 1) choose product 2 :n :n
end

repeat 15 [print catalan repcount]
Output:
1
1
2
5
14
42
132
429
1430
4862
16796
58786
208012
742900
2674440

Logtalk

For this task it is instructive to show a more general-purpose interface for sequences and an implementation of it for Catalan numbers.

First, loader.lgt:

:- initialization((
% libraries
% application
)).


The interface is defined in seqp.lgt as a protocol:

:- protocol(seqp).

:- public(init/0).    % reset to a beginning state if meaningful

:- public(nth/2).     % get the nth value of the sequence

:- public(to_nth/2).  % get from the start to the nth value of the sequence as a list

:- end_protocol.


The implementation of a Catalan sequence generator is in catalan.lgt:

:- object(catalan, implements(seqp)).

:- private(catalan/2).
:- dynamic(catalan/2).

% Public interface.

init :- retractall(catalan(_,_)).   % flush any memoized results

nth(N, V) :- \+ catalan(N, V), catalan_(N, V), !.   % generate iff it's not been memoized
nth(N, V) :- catalan(N, V), !.                      % otherwise use the memoized version

to_nth(N, L) :-
integer::sequence(0, N, S), % generate a list of 0 to N
meta::map(nth, S, L).       % map the nth/2 predicate to the list for all Catalan numbers up to N

% Local helper predicates.

catalan_(N, V) :-
N > 0,                              % calculate
N1 is N - 1,
N2 is N + 1,
catalan_(N1, V1),                   % via a recursive call
V is V1 * 2 * (2 * N - 1) // N2,
assertz(catalan(N, V)).             % and memoize the result
catalan_(0, 1).

:- end_object.


This is a memoizing implementation whose impact we will check in the test. The init/0 predicate flushes any memoized results.

The test driver is a simple one that generates the first fifteen Catalan numbers four times, comparing times with and without memoization. From catalan_test.lgt:

:- object(catalan_test).

:- public(run/0).

run :-
% put the object into a known initial state
catalan::init,

% first 15 Catalan numbers, record duration.
time_operation(catalan::to_nth(15, C1), D1),

% first 15 Catalan numbers again, twice, recording duration.
time_operation(catalan::to_nth(15, C2), D2),
time_operation(catalan::to_nth(15, C3), D3),

% reset the object again
catalan::init,

% first 15 Catalan numbers, record duration.
time_operation(catalan::to_nth(15, C4), D4),

% ensure the results were the same each time
C1 = C2, C2 = C3, C3 = C4,

% write the results and durations of each run
write(C1), write(' '), write(D1), nl,
write(C2), write(' '), write(D2), nl,
write(C3), write(' '), write(D3), nl,
write(C4), write(' '), write(D4), nl.
% visual inspection should show all results the same
% first and final durations should be much larger

:- meta_predicate(time_operation(0, *)).

time_operation(Goal, Duration) :-
time::cpu_time(Before),
call(Goal),
time::cpu_time(After),
Duration is After - Before.

:- end_object.


Output:

The session at the top-level looks like this:

?- {loader}.
% ... messages elided ...
% (0 warnings)
true.

?- catalan_test::run.
[1,1,2,5,14,42,132,429,1430,4862,16796,58786,208012,742900,2674440,9694845] 0.001603
[1,1,2,5,14,42,132,429,1430,4862,16796,58786,208012,742900,2674440,9694845] 0.000306
[1,1,2,5,14,42,132,429,1430,4862,16796,58786,208012,742900,2674440,9694845] 0.00026
[1,1,2,5,14,42,132,429,1430,4862,16796,58786,208012,742900,2674440,9694845] 0.001346
true.


This test shows:

1. The nth/2 predicate works (since to_nth/2 is implemented in terms of it).
2. The to_nth/2 predicate works.
3. Memoization generates a speedup of between ~4.5× to ~6.2× over generating from scratch.

Lua

-- recursive with memoization
local catalan = { [0] = 1 }
setmetatable(catalan, {
__index = function(c, n)
c[n] = c[n - 1] * 2 * (2 * n - 1) / (n + 1)
return c[n]
end
})

for i = 0, 14 do
print(string.format("%d", catalan[i]))
end

Output:
1
1
2
5
14
42
132
429
1430
4862
16796
58786
208012
742900
2674440

            NORMAL MODE IS INTEGER
DIMENSION C(15)

C(0) = 1
THROUGH CALC, FOR N=1, 1, N.GE.15
CALC        C(N) = ((4*N-2)*C(N-1))/(N+1)

THROUGH SHOW, FOR N=0, 1, N.GE.15
SHOW        PRINT FORMAT CFMT,N,C(N)

VECTOR VALUES CFMT=$2HC(,I2,4H) = ,I7*$
END OF PROGRAM
Output:
C( 0) =       1
C( 1) =       1
C( 2) =       2
C( 3) =       5
C( 4) =      14
C( 5) =      42
C( 6) =     132
C( 7) =     429
C( 8) =    1430
C( 9) =    4862
C(10) =   16796
C(11) =   58786
C(12) =  208012
C(13) =  742900
C(14) = 2674440

Maple

CatalanNumbers := proc( n::posint )
return seq( (2*i)!/((i + 1)!*i!), i = 0 .. n - 1 );
end proc:
CatalanNumbers(15);

Output:

1, 1, 2, 5, 14, 42, 132, 429, 1430, 4862, 16796, 58786, 208012, 742900, 2674440


Mathematica / Wolfram Language

CatalanN[n_Integer /; n >= 0] := (2 n)!/((n + 1)! n!)

Sample Output:
TableForm[CatalanN/@Range[0,15]]
//TableForm=
1
1
2
5
14
42
132
429
1430
4862
16796
58786
208012
742900
2674440
9694845


MATLAB / Octave

function n = catalanNumber(n)
for i = (1:length(n))
n(i) = (1/(n(i)+1))*nchoosek(2*n(i),n(i));
end
end


The following version computes at the same time the n first Catalan numbers (including C0).

function n = catalanNumbers(n)
n = [1 cumprod((2:4:4*n-6) ./ (2:n))];
end

Sample Output:
>> catalanNumber(14)

ans =

2674440

>> catalanNumbers(18)'

ans =

1
1
2
5
14
42
132
429
1430
4862
16796
58786
208012
742900
2674440
9694845
35357670
129644790


The following version uses the identity Ln(x!)=Gammaln(x+1) and prod(1:x)=sum(ln(1:x))

CatalanNumber=@(n) round(exp(gammaln(2*n+1)-sum(gammaln([n+2 n+1]))));

Sample Output:
>>CatalanNumber(10)

ans =

16796

>> num2str(CatalanNumber(20))

ans =

'6564120420'


Maxima

/* The following is an array function, hence the square brackets. It uses memoization automatically */
cata[n] := sum(cata[i]*cata[n - 1 - i], i, 0, n - 1)$cata[0]: 1$

cata2(n) := binomial(2*n, n)/(n + 1)$makelist(cata[n], n, 0, 14); makelist(cata2(n), n, 0, 14); /* both return [1, 1, 2, 5, 14, 42, 132, 429, 1430, 4862, 16796, 58786, 208012, 742900, 2674440] */  Miranda main :: [sys_message] main = [Stdout (lay (map (show . catalan) [0..14]))] catalan :: num->num catalan 0 = 1 catalan n = (4*n - 2) * catalan (n - 1) div (n + 1) Output: 1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440 Modula-2 MODULE CatalanNumbers; FROM FormatString IMPORT FormatString; FROM Terminal IMPORT WriteString,WriteLn,ReadChar; PROCEDURE binomial(m,n : LONGCARD) : LONGCARD; VAR r,d : LONGCARD; BEGIN r := 1; d := m - n; IF d>n THEN n := d; d := m - n; END; WHILE m>n DO r := r * m; DEC(m); WHILE (d>1) AND NOT (r MOD d # 0) DO r := r DIV d; DEC(d) END END; RETURN r END binomial; PROCEDURE catalan1(n : LONGCARD) : LONGCARD; BEGIN RETURN binomial(2*n,n) DIV (1+n) END catalan1; PROCEDURE catalan2(n : LONGCARD) : LONGCARD; VAR i,sum : LONGCARD; BEGIN IF n>1 THEN sum := 0; FOR i:=0 TO n-1 DO sum := sum + catalan2(i) * catalan2(n - 1 - i) END; RETURN sum ELSE RETURN 1 END END catalan2; PROCEDURE catalan3(n : LONGCARD) : LONGCARD; BEGIN IF n#0 THEN RETURN 2 *(2 * n - 1) * catalan3(n - 1) DIV (1 + n) ELSE RETURN 1 END END catalan3; VAR blah : LONGCARD = 123; buf : ARRAY[0..63] OF CHAR; i : LONGCARD; BEGIN FormatString("\tdirect\tsumming\tfrac\n", buf); WriteString(buf); FOR i:=0 TO 15 DO FormatString("%u\t%u\t%u\t%u\n", buf, i, catalan1(i), catalan2(i), catalan3(i)); WriteString(buf) END; ReadChar END CatalanNumbers.  Nim import math import strformat proc catalan1(n: int): int = binom(2 * n, n) div (n + 1) proc catalan2(n: int): int = if n == 0: return 1 for i in 0..<n: result += catalan2(i) * catalan2(n - 1 - i) proc catalan3(n: int): int = if n > 0: 2 * (2 * n - 1) * catalan3(n - 1) div (1 + n) else: 1 for i in 0..15: echo &"{i:7} {catalan1(i):7} {catalan2(i):7} {catalan3(i):7}"  Output:  0 1 1 1 1 1 1 1 2 2 2 2 3 5 5 5 4 14 14 14 5 42 42 42 6 132 132 132 7 429 429 429 8 1430 1430 1430 9 4862 4862 4862 10 16796 16796 16796 11 58786 58786 58786 12 208012 208012 208012 13 742900 742900 742900 14 2674440 2674440 2674440 15 9694845 9694845 9694845 OCaml let imp_catalan n = let return = ref 1 in for i = 1 to n do return := !return * 2 * (2 * i - 1) / (i + 1) done; !return let rec catalan = function | 0 -> 1 | n -> catalan (n - 1) * 2 * (2 * n - 1) / (n + 1) let memoize f = let cache = Hashtbl.create 20 in fun n -> match Hashtbl.find_opt cache n with | None -> let x = f n in Hashtbl.replace cache n x; x | Some x -> x let catalan_cache = Hashtbl.create 20 let rec memo_catalan n = if n = 0 then 1 else match Hashtbl.find_opt catalan_cache n with | None -> let x = memo_catalan (n - 1) * 2 * (2 * n - 1) / (n + 1) in Hashtbl.replace catalan_cache n x; x | Some x -> x let () = if not !Sys.interactive then let bench label f n times = let start = Unix.gettimeofday () in begin for i = 1 to times do f n done; let stop = Unix.gettimeofday () in Printf.printf "%s (%d runs) : %.3f\n" label times (stop -. start) end in let show f g h f' n = for i = 0 to n do Printf.printf "%2d %7d %7d %7d %7d\n" i (f i) (g i) (h i) (f' i) done in List.iter (fun (l, f) -> bench l f 15 10_000_000) ["imperative", imp_catalan; "recursive", catalan; "hand-memoized", memo_catalan; "memoized", (memoize catalan)]; show imp_catalan catalan memo_catalan (memoize catalan) 15  Output: $ ocaml unix.cma catalan.ml
imperative (10000000 runs) : 3.420
recursive (10000000 runs) : 3.821
hand-memoized (10000000 runs) : 0.531
memoized (10000000 runs) : 0.515
0       1       1       1       1
1       1       1       1       1
2       2       2       2       2
3       5       5       5       5
4      14      14      14      14
5      42      42      42      42
6     132     132     132     132
7     429     429     429     429
8    1430    1430    1430    1430
9    4862    4862    4862    4862
10   16796   16796   16796   16796
11   58786   58786   58786   58786
12  208012  208012  208012  208012
13  742900  742900  742900  742900
14 2674440 2674440 2674440 2674440
15 9694845 9694845 9694845 9694845

$ocamlopt -O2 unix.cmxa catalan.ml -o catalan$ ./catalan
imperative (10000000 runs) : 2.020
recursive (10000000 runs) : 2.283
hand-memoized (10000000 runs) : 0.159
memoized (10000000 runs) : 0.167
...

Oforth

: catalan( n -- m )
n ifZero: [ 1 ] else: [ catalan( n 1- ) 2 n * 1- * 2 * n 1+ / ] ;
Output:
import: mapping
seqFrom(0, 15) map( #catalan ) .
[1, 1, 2, 5, 14, 42, 132, 429, 1430, 4862, 16796, 58786, 208012, 742900, 2674440, 9694845]


ooRexx

Three versions of this.

loop i = 0 to 15
say "catI("i") =" .catalan~catI(i)
say "catR1("i") =" .catalan~catR1(i)
say "catR2("i") =" .catalan~catR2(i)
end

-- This is implemented as static members on a class object
-- so that the code is able to keep state information between calls.  This
-- memoization will speed up things like factorial calls by remembering previous
-- results.
::class catalan
-- initialize the class object
::method init class
expose facts catI catR1 catR2
facts = .table~new
catI = .table~new
catR1 = .table~new
catR2 = .table~new
-- seed a few items
facts[0] = 1
facts[1] = 1
facts[2] = 2
catI[0] = 1
catR1[0] = 1
catR2[0] = 1

-- private factorial method
::method fact private class
expose facts
use arg n
-- see if we've calculated this before
if facts~hasIndex(n) then return facts[n]
numeric digits 120

fact = 1
loop i = 2 to n
fact *= i
end
-- save this result
facts[n] = fact
return fact

::method catI class
expose catI
use arg n
numeric digits 20

res = catI[n]
if res == .nil then do
-- dividing by 1 removes insignificant trailing 0s
res = (self~fact(2 * n)/(self~fact(n + 1) * self~fact(n))) / 1
catI[n] = res
end
return res

::method catR1 class
expose catR1
use arg n
numeric digits 20

if catR1~hasIndex(n) then return catR1[n]
sum = 0
loop i = 0 to n - 1
sum += self~catR1(i) * self~catR1(n - 1 - i)
end
-- remove insignificant trailing 0s
sum = sum / 1
catR1[n] = sum
return sum

::method catR2 class
expose catR2
use arg n
numeric digits 20

res = catR2[n]
if res == .nil then do
res = ((2 * (2 * n - 1) * self~catR2(n - 1)) /  (n + 1))
catR2[n] = res
end
return res

Output:
catI(0) = 1
catR1(0) = 1
catR2(0) = 1
catI(1) = 1
catR1(1) = 1
catR2(1) = 1
catI(2) = 2
catR1(2) = 2
catR2(2) = 2
catI(3) = 5
catR1(3) = 5
catR2(3) = 5
catI(4) = 14
catR1(4) = 14
catR2(4) = 14
catI(5) = 42
catR1(5) = 42
catR2(5) = 42
catI(6) = 132
catR1(6) = 132
catR2(6) = 132
catI(7) = 429
catR1(7) = 429
catR2(7) = 429
catI(8) = 1430
catR1(8) = 1430
catR2(8) = 1430
catI(9) = 4862
catR1(9) = 4862
catR2(9) = 4862
catI(10) = 16796
catR1(10) = 16796
catR2(10) = 16796
catI(11) = 58786
catR1(11) = 58786
catR2(11) = 58786
catI(12) = 208012
catR1(12) = 208012
catR2(12) = 208012
catI(13) = 742900
catR1(13) = 742900
catR2(13) = 742900
catI(14) = 2674440
catR1(14) = 2674440
catR2(14) = 2674440
catI(15) = 9694845
catR1(15) = 9694845
catR2(15) = 9694845

PARI/GP

Memoization is not worthwhile; PARI has fast built-in facilities for calculating binomial coefficients and factorials.

catalan(n)=binomial(2*n,n+1)/n

A second version:

catalan(n)=(2*n)!/(n+1)!/n!

Naive version with binary splitting:

catalan(n)=prod(k=n+2,2*n,k)/prod(k=2,n,k)

Naive version:

catalan(n)={
my(t=1);
for(k=n+2,2*n,t*=k);
for(k=2,n,t/=k);
t
};

The first version takes about 1.5 seconds to compute the millionth Catalan number, while the second takes 3.9 seconds. The naive implementations, for comparison, take 21 and 45 minutes. In any case, printing the first 15 is simple:

vector(15,n,catalan(n))

Pascal

Program CatalanNumbers(output);

function catalanNumber1(n: integer): double;
begin
if n = 0 then
catalanNumber1 := 1.0
else
catalanNumber1 := double(4 * n - 2) / double(n + 1) * catalanNumber1(n-1);
end;

var
number: integer;

begin
writeln('Catalan Numbers');
writeln('Recursion with a fraction:');
for number := 0 to 14 do
writeln (number:3, round(catalanNumber1(number)):9);
end.

Output:
:> ./CatalanNumbers
Catalan Numbers
Recursion with a fraction:
0        1
1        1
2        2
3        5
4       14
5       42
6      132
7      429
8     1430
9     4862
10    16796
11    58786
12   208012
13   742900
14  2674440


Perl

sub factorial { my $f = 1;$f *= $_ for 2 ..$_[0]; $f; } sub catalan { my$n = shift;
factorial(2*$n) / factorial($n+1) / factorial($n); } print "$_\t@{[ catalan($_) ]}\n" for 0 .. 20;  For computing up to 20 ish, memoization is not needed. For much bigger numbers, this is faster: my @c = (1); sub catalan { use bigint;$c[$_[0]] //= catalan($_[0]-1) * (4 * $_[0]-2) / ($_[0]+1)
}

# most of the time is spent displaying the long numbers, actually
print "$_\t", catalan($_), "\n" for 0 .. 10000;


That has two downsides: high memory use and slow access to an isolated large value. Using a fast binomial function can solve both these issues. The downside here is if the platform doesn't have the GMP library then binomials won't be fast.

Library: ntheory
use ntheory qw/binomial/;
sub catalan {
my $n = shift; binomial(2*$n,$n)/($n+1);
}
print "$_\t", catalan($_), "\n" for 0 .. 10000;


Phix

with javascript_semantics
-- returns inf/-nan for n>85, and needs the rounding for n>=14, accurate to n=29
function catalan1(integer n)
return floor(factorial(2*n)/(factorial(n+1)*factorial(n))+0.5)
end function

-- returns inf for n>519, accurate to n=30:
function catalan2(integer n) -- NB: very slow!
atom res = not n
n -= 1
for i=0 to n do
res += catalan2(i)*catalan2(n-i)
end for
return res
end function

-- returns inf for n>514, accurate to n=30:
function catalan3(integer n)
if n=0 then return 1 end if
return 2*(2*n-1)/(1+n)*catalan3(n-1)
end function

sequence res = repeat(repeat(0,4),16),
times = repeat(0,3)
for t=1 to 4 do
atom t0 = time()
for i=0 to 15 do
switch t do
case 1: res[i+1][2] = catalan1(i)
case 2: res[i+1][3] = catalan2(i)
case 3: res[i+1][4] = catalan3(i)
case 4: res[i+1][1] = i; printf(1,"%2d: %10d %10d %10d\n",res[i+1])
end switch
end for
if t=4 then exit end if
times[t] = elapsed(time()-t0)
end for
printf(1,"times:%8s %10s %10s\n",times)

Output:
 0:          1          1          1
1:          1          1          1
2:          2          2          2
3:          5          5          5
4:         14         14         14
5:         42         42         42
6:        132        132        132
7:        429        429        429
8:       1430       1430       1430
9:       4862       4862       4862
10:      16796      16796      16796
11:      58786      58786      58786
12:     208012     208012     208012
13:     742900     742900     742900
14:    2674440    2674440    2674440
15:    9694845    9694845    9694845
times:      0s       1.6s         0s


As expected, catalan2() is by far the slowest, so let's memoise that one!

memoized recursive gmp version

Library: Phix/mpfr
with javascript_semantics
include builtins\mpfr.e

sequence c2cache = {}

function catalan2m(integer n)   -- very fast!
object r -- result (a [cached/shared] mpz)
-- (nb: modifying result will mess up cache)
if n<=0 then return mpz_init(1) end if
if n<=length(c2cache) then
r = c2cache[n]
if r!=0 then return r end if
else
c2cache &= repeat(0,n-length(c2cache))
end if
r = mpz_init(0)
mpz t = mpz_init()
for i=0 to n-1 do
mpz_mul(t,catalan2m(i),catalan2m(n-1-i))
end for
t = mpz_free(t)
c2cache[n] = r
return r
end function

sequence s = {}
for i=0 to 15 do s = append(s,mpz_get_str(catalan2m(i))) end for
printf(1,"0..15: %s\n",join(s,","))
printf(1,"100: %s\n",{mpz_get_str(catalan2m(100))})

Output:
0..15: 1,1,2,5,14,42,132,429,1430,4862,16796,58786,208012,742900,2674440,9694845
100: 896519947090131496687170070074100632420837521538745909320


PHP

<?php

{
private static $cache = array(0 => 1); private function fill_cache($i)
{
$accum = 0;$n = $i-1; for($k = 0; $k <=$n; $k++) {$accum += $this->item($k)*$this->item($n-$k); } self::$cache[$i] =$accum;
}
function item($i) { if (!isset(self::$cache[$i])) {$this->fill_cache($i); } return self::$cache[$i]; } }$cn = new CatalanNumbersSerie();
for($i = 0;$i <= 15;$i++) {$r = $cn->item($i);
echo "$i =$r\r\n";
}
?>

Output:
0 = 1
1 = 1
2 = 2
3 = 5
4 = 14
5 = 42
6 = 132
7 = 429
8 = 1430
9 = 4862
10 = 16796
11 = 58786
12 = 208012
13 = 742900
14 = 2674440
15 = 9694845

<?php
$n = 15;$t[1] = 1;
foreach (range(1, $n+1) as$i) {
foreach (range($i, 1-1) as$j) {
$t[$j] += $t[$j - 1];
}
$t[$i +1] = $t[$i];
foreach (range($i+1, 1-1) as$j) {
$t[$j] += $t[$j -1];
}
print ($t[$i+1]-$t[$i])."\t";
}

Output:
1	2	5	14	42	132	429	1430	4862	16796	58786	208012	742900	2674440	9694845	35357670


Picat

Works with: Picat
table
factorial(0) = 1.

factorial(N) = N * factorial(N - 1).

catalan1(N) = factorial(2 * N) // (factorial(N + 1) * factorial(N)).

catalan2(0) = 1.

catalan2(N) = 2 * (2 * N - 1) * catalan2(N - 1) // (N + 1).

main =>
foreach (I in 0..14)
printf("%d. %d = %d\n", I, catalan1(I), catalan2(I))
end.
Output:
0. 1 = 1
1. 1 = 1
2. 2 = 2
3. 5 = 5
4. 14 = 14
5. 42 = 42
6. 132 = 132
7. 429 = 429
8. 1430 = 1430
9. 4862 = 4862
10. 16796 = 16796
11. 58786 = 58786
12. 208012 = 208012
13. 742900 = 742900
14. 2674440 = 2674440


PicoLisp

# Factorial
(de fact (N)
(if (=0 N)
1
(* N (fact (dec N))) ) )

# Directly
(de catalanDir (N)
(/ (fact (* 2 N)) (fact (inc N)) (fact N)) )

# Recursively
(de catalanRec (N)
(if (=0 N)
1
(cache '(NIL) N  # Memoize
(sum
'((I) (* (catalanRec I) (catalanRec (- N I 1))))
(range 0 (dec N)) ) ) ) )

# Alternatively
(de catalanAlt (N)
(if (=0 N)
1
(*/ 2 (dec (* 2 N)) (catalanAlt (dec N)) (inc N)) ) )

# Test
(for (N 0 (> 15 N) (inc N))
(tab (2 4 8 8 8)
N
" => "
(catalanDir N)
(catalanRec N)
(catalanAlt N) ) )
Output:
 0 =>        1       1       1
1 =>        1       1       1
2 =>        2       2       2
3 =>        5       5       5
4 =>       14      14      14
5 =>       42      42      42
6 =>      132     132     132
7 =>      429     429     429
8 =>     1430    1430    1430
9 =>     4862    4862    4862
10 =>    16796   16796   16796
11 =>    58786   58786   58786
12 =>   208012  208012  208012
13 =>   742900  742900  742900
14 =>  2674440 2674440 2674440

PL/0

Translation of: Tiny BASIC

Integers are limited to 32767 so only the first ten Catalan numbers can be represented. To avoid internal overflow, the program subtracts something clever from c and then adds it back at the end.

var n, c, i;
begin
n := 0; c := 1;
! c;
while n <= 9 do
begin
n := n + 1;
i := 0;
while c > 0 do
begin
c := c - (n + 1);
i := i + 1
end;
c := 2 * (2 * n - 1) * c / (n + 1);
c := c + 2 * i * (2 * n - 1);
! c
end;
end.

Output:
       1
1
2
5
14
42
132
429
1430
4862
16796


PL/I

catalan: procedure options (main);   /* 23 February 2012 */
declare (i, n) fixed;

put skip list ('How many catalan numbers do you want?');
get list (n);

do i = 0 to n;
put skip list (c(i));
end;

c: procedure (n) recursive returns (fixed decimal (15));
declare n fixed;

if n <= 1 then return (1);

return ( 2*(2*n-1) * c(n-1) / (n + 1) );
end c;

end catalan;
Output:
How many catalan numbers do you want?

1
1
2
5
14
42
132
429
1430
4862
16796
58786
208012
742900
2674440
9694845
35357670
129644790
477638700
1767263190
6564120420


Plain TeX

\newcount\n
\newcount\r
\newcount\x
\newcount\ii

\def\catalan#1{%
\loop{%
\x\ii%
\multiply\x by 2 \advance\x by -1 \multiply\x by 2%
\global\multiply\r by\x%
\global\divide\r by\ii%
} \ifnum\number\ii<\n\repeat%
\the\r
}

\rightskip=0pt plus1fil\parindent=0pt
\loop{${\rm Catalan}(\the\x) = \catalan{\the\x}$\hfil\break}%

\bye


PowerShell

function Catalan([uint64]$m) { function fact([bigint]$n) {
if($n -lt 2) {[bigint]::one} else{2..$n | foreach -Begin {$prod = [bigint]::one} -Process {$prod = [bigint]::Multiply($prod,$_)} -End {$prod}} }$fact = fact $m$fact1 = [bigint]::Multiply($m+1,$fact)
[bigint]::divide((fact (2*$m)), [bigint]::Multiply($fact,$fact1)) } 0..15 | foreach {"catalan($_): $(catalan$_)"}


Output:

catalan(0): 1
catalan(1): 1
catalan(2): 2
catalan(3): 5
catalan(4): 14
catalan(5): 42
catalan(6): 132
catalan(7): 429
catalan(8): 1430
catalan(9): 4862
catalan(10): 16796
catalan(11): 58786
catalan(12): 208012
catalan(13): 742900
catalan(14): 2674440
catalan(15): 9694845


An Alternate Version

This version could easily be modified to work with big integers.

function Get-CatalanNumber
{
[CmdletBinding()]
[OutputType([PSCustomObject])]
Param
(
[Parameter(Mandatory=$true, ValueFromPipeline=$true,
ValueFromPipelineByPropertyName=$true, Position=0)] [uint32[]]$InputObject
)

Begin
{
function Get-Factorial ([int]$Number) { if ($Number -eq 0)
{
return 1
}

$factorial = 1 1..$Number | ForEach-Object {$factorial *=$_}

$factorial } function Get-Catalan ([int]$Number)
{
if ($Number -eq 0) { return 1 } (Get-Factorial (2 *$Number)) / ((Get-Factorial (1 + $Number)) * (Get-Factorial$Number))
}
}
Process
{
foreach ($number in$InputObject)
{
[PSCustomObject]@{
Number        = $number CatalanNumber = Get-Catalan$number
}
}
}
}


Get the first fifteen Catalan numbers as a PSCustomObject:

0..14 | Get-CatalanNumber

Output:
Number CatalanNumber
------ -------------
0             1
1             1
2             2
3             5
4            14
5            42
6           132
7           429
8          1430
9          4862
10         16796
11         58786
12        208012
13        742900
14       2674440


To return only the array of Catalan numbers:

(0..14 | Get-CatalanNumber).CatalanNumber

Output:
1
1
2
5
14
42
132
429
1430
4862
16796
58786
208012
742900
2674440


Prolog

Works with: SWI-Prolog
catalan(N) :-
length(L1, N),
L = [1 | L1],
init(1,1,L1),
numlist(0, N, NL),
maplist(my_write, NL, L).

init(_, _, []).

init(V, N, [H | T]) :-
N1 is N+1,
H is 2 * (2 * N - 1) * V / N1,
init(H, N1, T).

my_write(N, V) :-
format('~w : ~w~n', [N, V]).

Output:
 ?- catalan(15).
0 : 1
1 : 1
2 : 2
3 : 5
4 : 14
5 : 42
6 : 132
7 : 429
8 : 1430
9 : 4862
10 : 16796
11 : 58786
12 : 208012
13 : 742900
14 : 2674440
15 : 9694845
true .


Python

Three algorithms including explicit memoization. (Pythons factorial built-in function is not memoized internally).

Python will transparently switch to bignum-type integer arithmetic, so the code below works unchanged on computing larger catalan numbers such as cat(50) and beyond.

Works with: Python version 3
from math import factorial
import functools

def memoize(func):
cache = {}

def memoized(key):
# Returned, new, memoized version of decorated function
if key not in cache:
cache[key] = func(key)
return cache[key]
return functools.update_wrapper(memoized, func)

@memoize
def fact(n):
return factorial(n)

def cat_direct(n):
return fact(2 * n) // fact(n + 1) // fact(n)

@memoize
def catR1(n):
return 1 if n == 0 else (
sum(catR1(i) * catR1(n - 1 - i) for i in range(n))
)

@memoize
def catR2(n):
return 1 if n == 0 else (
((4 * n - 2) * catR2(n - 1)) // (n + 1)
)

if __name__ == '__main__':
def pr(results):
fmt = '%-10s %-10s %-10s'
print((fmt % tuple(c.__name__ for c in defs)).upper())
print(fmt % (('=' * 10,) * 3))
for r in zip(*results):
print(fmt % r)

defs = (cat_direct, catR1, catR2)
results = [tuple(c(i) for i in range(15)) for c in defs]
pr(results)

Sample Output:
CAT_DIRECT CATR1      CATR2
========== ========== ==========
1          1          1
1          1          1
2          2          2
5          5          5
14         14         14
42         42         42
132        132        132
429        429        429
1430       1430       1430
4862       4862       4862
16796      16796      16796
58786      58786      58786
208012     208012     208012
742900     742900     742900
2674440    2674440    2674440

The third definition is directly expressible, as an infinite series, in terms of itertools.accumulate:

'''Catalan numbers'''

from itertools import accumulate, chain, count, islice

# catalans3 :: [Int]
def catalans3():
'''Infinite sequence of Catalan numbers
'''
def go(c, n):
return 2 * c * pred(2 * n) // succ(n)

return accumulate(
chain([1], count(1)), go
)

# ------------------------- TEST -------------------------
# main :: IO ()
def main():
'''Catalan numbers, definition 3'''
print("Catalans 1-15:\n")
print(
'\n'.join([
f'{n:>10}' for n
in islice(catalans3(), 15)
])
)

# ----------------------- GENERIC ------------------------

# pred :: Int -> Int
def pred(n):
'''Predecessor function'''
return n - 1

# succ :: Int -> Int
def succ(n):
'''Successor function'''
return 1 + n

# MAIN ---
if __name__ == '__main__':
main()

Output:
Catalans 1-15:

1
1
2
5
14
42
132
429
1430
4862
16796
58786
208012
742900
2674440

Quackery

  [ 1 over times [ over i 1+ + * ] nip ] is 2n!/n!  ( n --> n )

[ times [ i 1+ / ] ]                   is /n!     ( n --> n )

[ dup 2n!/n! swap 1+ /n! ]             is catalan ( n --> n )

15 times [ i^  dup echo say " : " catalan echo cr ]
Output:
0 : 1
1 : 1
2 : 2
3 : 5
4 : 14
5 : 42
6 : 132
7 : 429
8 : 1430
9 : 4862
10 : 16796
11 : 58786
12 : 208012
13 : 742900
14 : 2674440


R

catalan <- function(n) choose(2*n, n)/(n + 1)
catalan(0:15)
[1]       1       1       2       5      14      42     132     429    1430
[10]    4862   16796   58786  208012  742900 2674440 9694845


Racket

#lang racket
(require planet2)
; (install "this-and-that")  ; uncomment to install
(require memoize/memo)

(define/memo* (catalan m)
(if (= m 0)
1
(for/sum ([i m])
(* (catalan i) (catalan (- m i 1))))))

(map catalan (range 1 15))

Output:
'(1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440)


Raku

(formerly Perl 6)

Works with: Rakudo version 2015.12

The recursive formulas are easily written into a constant array, either:

constant Catalan = 1, { [+] @_ Z* @_.reverse } ... *;


or

constant Catalan = 1, |[\*] (2, 6 ... *) Z/ 2 .. *;

# In both cases, the sixteen first values can be seen with:
.say for Catalan[^16];
Output:
1
1
2
5
14
42
132
429
1430
4862
16796
58786
208012
742900
2674440

REXX

version 1

All four methods of calculate the Catalan numbers use independent memoization for the computation of factorials.

In the 1st equation, the 2nd version's denominator:

(n+1)! n!

has been rearranged to:

(n+1) * [fact(n) **2]
/*REXX program calculates and displays  Catalan numbers  using  four different methods. */
parse arg LO HI .                                /*obtain optional arguments from the CL*/
if LO=='' | LO==","  then do;  HI=15; LO=0;  end /*No args? Then use a range of 0 ──► 15*/
if HI=='' | HI==","  then      HI=LO             /*No HI?   Then use  LO for the default*/
numeric digits max(20, 5*HI)                     /*this allows gihugic Catalan numbers. */
w=length(HI)                                     /*W:  is used for aligning the output. */
call hdr 1A;  do j=LO  to HI;  say '     Catalan'     right(j, w)": "      Cat1A(j);   end
call hdr 1B;  do j=LO  to HI;  say '     Catalan'     right(j, w)": "      Cat1B(j);   end
call hdr 2 ;  do j=LO  to HI;  say '     Catalan'     right(j, w)": "      Cat2(j) ;   end
call hdr 3 ;  do j=LO  to HI;  say '     Catalan'     right(j, w)": "      Cat3(j) ;   end
exit                                             /*stick a fork in it,  we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
!:     arg z; if !.z\==. then return !.z; !=1;  do k=2  to z; !=!*k; end;  !.z=!; return !
Cat1A: procedure expose !.;  parse arg n;     return comb(n+n, n)    %  (n+1)
Cat1B: procedure expose !.;  parse arg n;     return !(n+n) % ((n+1) * !(n)**2)
Cat3:  procedure expose c.;  arg n; if c.n==. then c.n=(4*n-2)*cat3(n-1)%(n+1); return c.n
comb:  procedure;            parse arg x,y;   return pFact(x-y+1, x) % pFact(2, y)
hdr:   !.=.; c.=.; c.0=1; say; say center('Catalan numbers, method' arg(1),79,'─'); return
pFact: procedure;            !=1;      do k=arg(1)  to arg(2);  !=!*k;  end;    return !
/*──────────────────────────────────────────────────────────────────────────────────────*/
Cat2:  procedure expose c.;  parse arg n;  $=0; if c.n\==. then return c.n do k=0 for n;$=$+ Cat2(k) * Cat2(n-k-1); end c.n=$;           return $/*use a memoization technique.*/ output when using the input of: 0 16 ───────────────────────── Catalan numbers, method 1A ────────────────────────── Catalan 0: 1 Catalan 1: 1 Catalan 2: 2 Catalan 3: 5 Catalan 4: 14 Catalan 5: 42 Catalan 6: 132 Catalan 7: 429 Catalan 8: 1430 Catalan 9: 4862 Catalan 10: 16796 Catalan 11: 58786 Catalan 12: 208012 Catalan 13: 742900 Catalan 14: 2674440 Catalan 15: 9694845 ───────────────────────── Catalan numbers, method 1B ────────────────────────── ··· (elided, same as first method) ··· ───────────────────────── Catalan numbers, method 2 ────────────────────────── ··· (elided, same as first method) ··· ───────────────────────── Catalan numbers, method 3 ────────────────────────── ··· (elided, same as first method) ···  Timing notes of the four methods: • For Catalan numbers 1 ──► 200: • method 1A is about 50 times slower than method 3 • method 1B is about 100 times slower than method 3 • method 2 is about 85 times slower than method 3 • For Catalan numbers 1 ──► 300: • method 1A is about 100 times slower than method 3 • method 1B is about 200 times slower than method 3 • method 2 is about 200 times slower than method 3 Method 3 is really quite fast; even in the thousands range, computation time is still quite reasonable. version 2 Implements the 3 methods shown in the task description /* REXX --------------------------------------------------------------- * 01.07.2014 Walter Pachl *--------------------------------------------------------------------*/ Numeric Digits 1000 Parse Arg m . If m='' Then m=20 Do i=0 To m c1.i=c1(i) End c2.=1 Do i=1 To m c2.i=c2(i) End c3.=1 Do i=1 To m im1=i-1 c3.i=2*(2*i-1)*c3.im1/(i+1) End l=length(c3.m) hdr=' n' right('c1.n',l), right('c2.n',l), right('c3.n',l) Say hdr Do i=0 To m Say right(i,2) format(c1.i,l), format(c2.i,l), format(c3.i,l) End Say hdr Exit c1: Procedure Parse Arg n return fact(2*n)/(fact(n)*fact(n+1)) c2: Procedure Expose c2. Parse Arg n res=0 Do i=0 To n-1 nmi=n-i-1 res=res+c2.i*c2.nmi End Return res fact: Procedure Parse Arg n f=1 Do i=1 To n f=f*i End Return f Output:  n c1.n c2.n c3.n 0 1 1 1 1 1 1 1 2 2 2 2 3 5 5 5 4 14 14 14 5 42 42 42 6 132 132 132 7 429 429 429 8 1430 1430 1430 9 4862 4862 4862 10 16796 16796 16796 11 58786 58786 58786 12 208012 208012 208012 13 742900 742900 742900 14 2674440 2674440 2674440 15 9694845 9694845 9694845 16 35357670 35357670 35357670 17 129644790 129644790 129644790 18 477638700 477638700 477638700 19 1767263190 1767263190 1767263190 20 6564120420 6564120420 6564120420 n c1.n c2.n c3.n Ring for n = 1 to 15 see catalan(n) + nl next func catalan n if n = 0 return 1 ok cat = 2 * (2 * n - 1) * catalan(n - 1) / (n + 1) return cat Output: 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440 9694845  RPL Works with: Halcyon Calc version 4.2.7 Code Comments ≪ IFERR R→B THEN END IF DUP #1 ≠ THEN DUP 2 * 1 - 2 * OVER 1 - →CAT * SWAP 1 + / END ≫ '→CAT' STO  ( n -- C(n) ) Ignore the conversion error if n is already a binary integer C(1) = 1 Divide by (n+1) at the end to stay in the integer world  To speed up execution, additions can be preferred to multiplications by replacing 2 * with DUP +. The following piece of code will deliver what is required: ≪ 1 { } DO OVER →CAT B→R + SWAP 1 + SWAP UNTIL OVER 15 > END ≫ EVAL  Output: 1: { 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440 9694845 }  Ruby def factorial(n) (1..n).reduce(1, :*) end # direct def catalan_direct(n) factorial(2*n) / (factorial(n+1) * factorial(n)) end # recursive def catalan_rec1(n) return 1 if n == 0 (0...n).sum{|i| catalan_rec1(i) * catalan_rec1(n-1-i)} end def catalan_rec2(n) return 1 if n == 0 2*(2*n - 1) * catalan_rec2(n-1) / (n+1) end # performance and results require 'benchmark' require 'memoize' include Memoize Benchmark.bm(17) do |b| b.report('catalan_direct') {16.times {|n| catalan_direct(n)} } b.report('catalan_rec1') {16.times {|n| catalan_rec1(n)} } b.report('catalan_rec2') {16.times {|n| catalan_rec2(n)} } memoize :catalan_rec1 b.report('catalan_rec1(memo)'){16.times {|n| catalan_rec1(n)} } end puts "\n direct rec1 rec2" 16.times {|n| puts "%2d :%9d%9d%9d" % [n, catalan_direct(n), catalan_rec1(n), catalan_rec2(n)]} The output shows the dramatic difference memoizing makes.  user system total real catalan_direct 0.000000 0.000000 0.000000 ( 0.000124) catalan_rec1 6.178000 0.000000 6.178000 ( 6.195141) catalan_rec2 0.000000 0.000000 0.000000 ( 0.000023) catalan_rec1(memo) 0.000000 0.000000 0.000000 ( 0.000641) direct rec1 rec2 0 : 1 1 1 1 : 1 1 1 2 : 2 2 2 3 : 5 5 5 4 : 14 14 14 5 : 42 42 42 6 : 132 132 132 7 : 429 429 429 8 : 1430 1430 1430 9 : 4862 4862 4862 10 : 16796 16796 16796 11 : 58786 58786 58786 12 : 208012 208012 208012 13 : 742900 742900 742900 14 : 2674440 2674440 2674440 15 : 9694845 9694845 9694845  Rust fn c_n(n: u64) -> u64 { match n { 0 => 1, _ => c_n(n - 1) * 2 * (2 * n - 1) / (n + 1) } } fn main() { for i in 1..16 { println!("c_n({}) = {}", i, c_n(i)); } } Output: c(1) = 1 c(2) = 2 c(3) = 5 c(4) = 14 c(5) = 42 c(6) = 132 c(7) = 429 c(8) = 1430 c(9) = 4862 c(10) = 16796 c(11) = 58786 c(12) = 208012 c(13) = 742900 c(14) = 2674440 c(15) = 9694845 Scala Simple and straightforward. Noticeably out of steam without memoizing at about 5000. object CatalanNumbers { def main(args: Array[String]): Unit = { for (n <- 0 to 15) { println("catalan(" + n + ") = " + catalan(n)) } } def catalan(n: BigInt): BigInt = factorial(2 * n) / (factorial(n + 1) * factorial(n)) def factorial(n: BigInt): BigInt = BigInt(1).to(n).foldLeft(BigInt(1))(_ * _) } Output: catalan(0) = 1 catalan(1) = 1 catalan(2) = 2 catalan(3) = 5 catalan(4) = 14 catalan(5) = 42 catalan(6) = 132 catalan(7) = 429 catalan(8) = 1430 catalan(9) = 4862 catalan(10) = 16796 catalan(11) = 58786 catalan(12) = 208012 catalan(13) = 742900 catalan(14) = 2674440 catalan(15) = 9694845  Scheme Tail recursive implementation. (define (catalan m) (let loop ((c 1)(n 0)) (if (not (eqv? n m)) (begin (display n)(display ": ")(display c)(newline) (loop (* (/ (* 2 (- (* 2 (+ n 1)) 1)) (+ (+ n 1) 1)) c) (+ n 1) ))))) (catalan 15) Output: 0: 1 1: 1 2: 2 3: 5 4: 14 5: 42 6: 132 7: 429 8: 1430 9: 4862 10: 16796 11: 58786 12: 208012 13: 742900 14: 2674440 Seed7 $ include "seed7_05.s7i";
include "bigint.s7i";

const proc: main is func
local
var bigInteger: n is 0_;
begin
for n range 0_ to 15_ do
writeln((2_ * n) ! n div succ(n));
end for;
end func;
Output:
1
1
2
5
14
42
132
429
1430
4862
16796
58786
208012
742900
2674440
9694845


Sidef

func f(i) { i==0 ? 1 : (i * f(i-1)) }
func c(n) { f(2*n) / f(n) / f(n+1) }

With memoization:

func c(n) is cached {
n == 0 ? 1 : (c(n-1) * (4 * n - 2) / (n + 1))
}

Calling the function:

15.times { |i|
say "#{i}\t#{c(i)}"
}
Output:
0	1
1	1
2	2
3	5
4	14
5	42
6	132
7	429
8	1430
9	4862
10	16796
11	58786
12	208012
13	742900
14	2674440


Standard ML

(*
* val catalan : int -> int
* Returns the nth Catalan number.
*)
fun catalan 0 = 1
|   catalan n = ((4 * n - 2) * catalan(n - 1)) div (n + 1);

(*
* val print_catalans : int -> unit
* Prints out Catalan numbers 0 through 15.
*)
fun print_catalans(n) =
if n > 15 then ()
else (print (Int.toString(catalan n) ^ "\n"); print_catalans(n + 1)); print_catalans(0);
(*
* 1
* 1
* 2
* 5
* 14
* 42
* 132
* 429
* 1430
* 4862
* 16796
* 58786
* 208012
* 742900
* 2674440
* 9694845
*)

Stata

clear
set obs 15
gen catalan=1 in 1
replace catalan=catalan[_n-1]*2*(2*_n-3)/_n in 2/l
list, noobs noh

Output

  +---------+
|       1 |
|       1 |
|       2 |
|       5 |
|      14 |
|---------|
|      42 |
|     132 |
|     429 |
|    1430 |
|    4862 |
|---------|
|   16796 |
|   58786 |
|  208012 |
|  742900 |
| 2674440 |
+---------+

Swift

Translation of: Rust
func catalan(_ n: Int) -> Int {
switch n {
case 0:
return 1
case _:
return catalan(n - 1) * 2 * (2 * n - 1) / (n + 1)
}
}

for i in 1..<16 {
print("catalan(\(i)) => \(catalan(i))")
}
Output:
catalan(1) => 1
catalan(2) => 2
catalan(3) => 5
catalan(4) => 14
catalan(5) => 42
catalan(6) => 132
catalan(7) => 429
catalan(8) => 1430
catalan(9) => 4862
catalan(10) => 16796
catalan(11) => 58786
catalan(12) => 208012
catalan(13) => 742900
catalan(14) => 2674440
catalan(15) => 9694845


Tcl

package require Tcl 8.5

# Memoization wrapper
proc memoize {function value generator} {
variable memoize
set key $function,$value
if {![info exists memoize($key)]} { set memoize($key) [uplevel 1 $generator] } return$memoize($key) } # The simplest recursive definition proc tcl::mathfunc::catalan n { if {[incr n 0] < 0} {error "must not be negative"} memoize catalan$n {expr {
$n == 0 ? 1 : 2 * (2*$n - 1) * catalan($n - 1) / ($n + 1)
}}
}

Demonstration:

for {set i 0} {$i < 15} {incr i} { puts "C_$i = [expr {catalan($i)}]" } Output: C_0 = 1 C_1 = 1 C_2 = 2 C_3 = 5 C_4 = 14 C_5 = 42 C_6 = 132 C_7 = 429 C_8 = 1430 C_9 = 4862 C_10 = 16796 C_11 = 58786 C_12 = 208012 C_13 = 742900 C_14 = 2674440  Of course, this code also works unchanged (apart from extending the loop) for producing higher Catalan numbers. For example, here is the end of the output when asked to produce the first fifty: C_45 = 2257117854077248073253720 C_46 = 8740328711533173390046320 C_47 = 33868773757191046886429490 C_48 = 131327898242169365477991900 C_49 = 509552245179617138054608572  TypeScript Translation of: GW-BASIC // Catalan numbers var c: number[] = [1]; console.log(${0}\t${c[0]}); for (n = 0; n < 15; n++) { c[n + 1] = 0; for (i = 0; i <= n; i++) c[n + 1] = c[n + 1] + c[i] * c[n - i]; console.log(${n + 1}\t\${c[n + 1]});
}
Output:
0	1
1	1
2	2
3	5
4	14
5	42
6	132
7	429
8	1430
9	4862
10	16796
11	58786
12	208012
13	742900
14	2674440
15	9694845


Ursala

#import std
#import nat

catalan = quotient^\successor choose^/double ~&

#cast %nL

t = catalan* iota 16
Output:
<
1,
1,
2,
5,
14,
42,
132,
429,
1430,
4862,
16796,
58786,
208012,
742900,
2674440,
9694845>

Vala

namespace CatalanNumbers {
public class CatalanNumberGenerator {
private static double factorial(double n) {
if (n == 0)
return 1;
return n * factorial(n - 1);
}

public double first_method(double n) {
const double top_multiplier = 2;
return factorial(top_multiplier * n) / (factorial(n + 1) * factorial(n));
}

public double second_method(double n) {
if (n == 0) {
return 1;
}
double sum = 0;
double i = 0;
for (; i <= (n - 1); i++) {
sum += second_method(i) * second_method((n - 1) - i);
}
return sum;
}

public double third_method(double n) {
if (n == 0) {
return 1;
}
return ((2 * (2 * n - 1)) / (n + 1)) * third_method(n - 1);
}
}

void main() {
CatalanNumberGenerator generator = new CatalanNumberGenerator();
DateTime initial_time;
DateTime final_time;
TimeSpan ts;

stdout.printf("Direct Method\n");
stdout.printf(" n%9s\n", "C_n");
stdout.printf("............\n");
initial_time = new DateTime.now();
for (double i = 0; i <= 15; i++) {
stdout.printf("%2s %8s\n", i.to_string(), Math.ceil(generator.first_method(i)).to_string());
}
final_time = new DateTime.now();
ts = final_time.difference(initial_time);
stdout.printf("............\n");
stdout.printf("Time Elapsed: %s μs\n", ts.to_string());

stdout.printf("\nRecursive Method 1\n");
stdout.printf(" n%9s\n", "C_n");
stdout.printf("............\n");
initial_time = new DateTime.now();
for (double i = 0; i <= 15; i++) {
stdout.printf("%2s %8s\n", i.to_string(), Math.ceil(generator.second_method(i)).to_string());
}
final_time = new DateTime.now();
ts = final_time.difference(initial_time);
stdout.printf("............\n");
stdout.printf("Time Elapsed: %s μs\n", ts.to_string());

stdout.printf("\nRecursive Method 2\n");
stdout.printf(" n%9s\n", "C_n");
stdout.printf("............\n");
initial_time = new DateTime.now();
for (double i = 0; i <= 15; i++) {
stdout.printf("%2s %8s\n", i.to_string(), Math.ceil(generator.third_method(i)).to_string());
}
final_time = new DateTime.now();
ts = final_time.difference(initial_time);
stdout.printf("............\n");
stdout.printf("Time Elapsed: %s μs\n", ts.to_string());

}
}
Output:
Direct Method
n      C_n
............
0        1
1        1
2        2
3        5
4       14
5       42
6      132
7      429
8     1430
9     4862
10    16796
11    58786
12   208012
13   742900
14  2674440
15  9694845
............
Time Elapsed: 132 μs

Recursive Method 1
n      C_n
............
0        1
1        1
2        2
3        5
4       14
5       42
6      132
7      429
8     1430
9     4862
10    16796
11    58786
12   208012
13   742900
14  2674440
15  9694845
............
Time Elapsed: 130430 μs

Recursive Method 2
n      C_n
............
0        1
1        1
2        2
3        5
4       14
5       42
6      132
7      429
8     1430
9     4862
10    16796
11    58786
12   208012
13   742900
14  2674440
15  9694845
............
Time Elapsed: 76 μs


V (Vlang)

Translation of: Go
import math.big

fn main() {
mut b:= big.zero_int
for n := i64(0); n < 15; n++ {
b = big.integer_from_i64(n)
b = (b*big.two_int).factorial()/(b.factorial()*(b*big.two_int-b).factorial())
println(b/big.integer_from_i64(n+1))
}
}
Output:
 1
1
2
5
14
42
132
429
1430
4862
16796
58786
208012
742900
2674440


Wortel

; the following number expression calculcates the nth Catalan number
#~ddiFSFmSoFSn
; which stands for: dup dup inc fac swap fac mult swap double fac swap divide
; to get the first 15 Catalan numbers we map this function over a list from 0 to 15
!*#~ddiFSFmSoFSn @til 15
; returns [1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674439.9999999995]

Wren

Library: Wren-fmt
Library: Wren-math
import "./fmt" for Fmt
import "./math" for Int

var catalan = Fn.new { |n|
if (n < 0) Fiber.abort("Argument must be a non-negative integer")
var prod = 1
var i = n + 2
while (i <= n * 2) {
prod = prod * i
i = i + 1
}
return prod / Int.factorial(n)
}

var catalanRec
catalanRec = Fn.new { |n| (n != 0) ? 2 * (2 * n - 1) * catalanRec.call(n - 1) / (n + 1) : 1 }

System.print(" n  Catalan number")
System.print("------------------")
for (i in 0..15) System.print("%(Fmt.d(2, i))  %(catalan.call(i))")
System.print("\nand again using a recursive function:\n")
for (i in 0..15) System.print("%(Fmt.d(2, i))  %(catalanRec.call(i))")
Output:
 n  Catalan number
------------------
0  1
1  1
2  2
3  5
4  14
5  42
6  132
7  429
8  1430
9  4862
10  16796
11  58786
12  208012
13  742900
14  2674440
15  9694845

and again using a recursive function:

0  1
1  1
2  2
3  5
4  14
5  42
6  132
7  429
8  1430
9  4862
10  16796
11  58786
12  208012
13  742900
14  2674440
15  9694845


XLISP

(defun catalan (n)
(if (= n 0)
1
(* (/ (* 2 (- (* 2 n) 1)) (+ n 1)) (catalan (- n 1))) ) )

(defun range (x y)
(cons x
(if (< x y)
(range (+ x 1) y) ) ) )

(print (mapcar catalan (range 0 14)))
Output:
(1 1 2 5 14 42 132 429 1430 4862 16796 58786 208012 742900 2674440)

XPL0

code CrLf=9, IntOut=11;
int  C, N;
[C:= 1;
IntOut(0, C);  CrLf(0);
for N:= 1 to 14 do
[C:= C*2*(2*N-1)/(N+1);
IntOut(0, C);  CrLf(0);
];
]
Output:
1
1
2
5
14
42
132
429
1430
4862
16796
58786
208012
742900
2674440


zkl

Uses GMP to calculate big factorials.

var BN=Import("zklBigNum");
fcn catalan(n){
BN(2*n).factorial() / BN(n+1).factorial() / BN(n).factorial();
}

foreach n in (16){
println("%2d --> %,d".fmt(n, catalan(n)));
}
println("%2d --> %,d".fmt(100, catalan(100)));

And an iterative solution at works up to the limit of 64 bit ints (n=33). Would be 35 but need to avoid factional intermediate results.

fcn catalan(n){ (1).reduce(n,fcn(p,n){ 2*(2*n-1)*p/(n+1) },1) }
Output:
 0 --> 1
1 --> 1
2 --> 2
3 --> 5
4 --> 14
5 --> 42
6 --> 132
7 --> 429
8 --> 1,430
9 --> 4,862
10 --> 16,796
11 --> 58,786
12 --> 208,012
13 --> 742,900
14 --> 2,674,440
15 --> 9,694,845
100 --> 896,519,947,090,131,496,687,170,070,074,100,632,420,837,521,538,745,909,320


ZX Spectrum Basic

Translation of: C
10 FOR i=0 TO 15
20 LET n=i: LET m=2*n
30 LET r=1: LET d=m-n
40 IF d>n THEN LET n=d: LET d=m-n
50 IF m<=n THEN GO TO 90
60 LET r=r*m: LET m=m-1
70 IF (d>1) AND NOT FN m(r,d) THEN LET r=r/d: LET d=d-1: GO TO 70
80 GO TO 50
90 PRINT i;TAB 4;r/(1+n)
100 NEXT i
110 STOP
120 DEF FN m(a,b)=a-INT (a/b)*b: REM Modulus function