Iccanobif primes
Iccanobif primes is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.
Iccanobif primes are prime numbers that, when reversed, are a Fibonacci number.
- Task
- Find and display the first 10 iccanobif primes.
- Stretch
- Find and display the digit count of the next 15 iccanobif primes.
- See also
ALGOL 68
BEGIN # show the first 10 prime Iccanobif (reversed Fibonacci) numbers #
# returns n with the digits reversed #
OP REVERSE = ( INT n )INT:
BEGIN
INT reverse := 0;
INT v := ABS n;
WHILE v > 0 DO
reverse *:= 10 +:= v MOD 10;
v OVERAB 10
OD;
reverse * SIGN n
END # REVERSE # ;
# returns TRUE if n is prime, FALSE otherwise - uses trial division #
PROC is prime = ( LONG INT n )BOOL:
IF n < 3 THEN n = 2
ELIF n MOD 3 = 0 THEN n = 3
ELIF NOT ODD n THEN FALSE
ELSE
BOOL is a prime := TRUE;
INT f := 5;
INT f2 := 25;
INT to next := 24;
WHILE f2 <= n AND is a prime DO
is a prime := n MOD f /= 0;
f +:= 2;
f2 +:= to next;
to next +:= 8
OD;
is a prime
FI # is prime # ;
# task #
INT p count := 0;
INT prev := 0;
INT curr := 1;
WHILE p count < 10 DO
INT next = prev + curr;
prev := curr;
curr := next;
INT rev := REVERSE curr;
IF is prime( rev ) THEN
# have a prime iccanobif number #
p count +:= 1;
print( ( " ", whole( rev, 0 ) ) )
FI
OD
END
- Output:
2 3 5 31 43 773 7951 64901 52057 393121
Python
""" rosettacode.org/wiki/Iccanobif_primes """
from sympy import isprime
def iccanobifs(wanted):
""" Print the series of iccanobif prime numbers up to wanted """
fib, prev, prevprev, fcount = 0, 1, 0, 0
print('First 30 Iccanobif primes:')
while fcount < wanted:
fib = prev + prevprev
prevprev = prev
prev = fib
dig = [int(c) for c in str(fib)]
candidate = sum(n * 10**i for i, n in enumerate(dig))
if isprime(candidate):
fcount += 1
dlen = len(str(candidate))
if dlen < 90:
print(candidate, f"({dlen} digit{'' if dlen == 1 else 's'})")
else:
s = str(candidate)
print(s[:30], "...", s[-29:], f'({dlen} digits)')
iccanobifs(30)
- Output:
First 30 Iccanobif primes: 2 (1 digit) 3 (1 digit) 5 (1 digit) 31 (2 digits) 43 (2 digits) 773 (3 digits) 7951 (4 digits) 64901 (5 digits) 52057 (5 digits) 393121 (6 digits) 56577108676171 (14 digits) 940647607443258103531 (21 digits) 5237879497657222310489731409575442761 (37 digits) 9026258083384996860449366072142307801963 (40 digits) 19900335674812302969315720344396951060628175943800862267761734431012073266446403 (80 digits) 778411373629674799853537498387 ... 06414225852312097783685331923 (104 digits) 377225859015676041888905465423 ... 42640418929174997072830756131 (137 digits) 757361938948761315956093082097 ... 05343825250767238644714305761 (330 digits) 178903368473328376208382371633 ... 39766460613175300695235035913 (406 digits) 923271631017291153059188123189 ... 39342926827061468856047302507 (409 digits) 504201578106980562530763299184 ... 34364678167335124247362214481 (503 digits) 305110124747393800923565587415 ... 27995099969296158361330018201 (888 digits) 468185470426936945550027667953 ... 73037342708664543144645856321 (1020 digits) 871013478530378198843208828928 ... 72170748420128396998865227391 (1122 digits) First 30 Iccanobif primes: 2 (1 digit) 3 (1 digit) 5 (1 digit) 31 (2 digits) 43 (2 digits) 773 (3 digits) 7951 (4 digits) 64901 (5 digits) 52057 (5 digits) 393121 (6 digits) 56577108676171 (14 digits) 940647607443258103531 (21 digits) 5237879497657222310489731409575442761 (37 digits) 9026258083384996860449366072142307801963 (40 digits) 19900335674812302969315720344396951060628175943800862267761734431012073266446403 (80 digits) 778411373629674799853537498387 ... 06414225852312097783685331923 (104 digits) 377225859015676041888905465423 ... 42640418929174997072830756131 (137 digits) 757361938948761315956093082097 ... 05343825250767238644714305761 (330 digits) 178903368473328376208382371633 ... 39766460613175300695235035913 (406 digits) 923271631017291153059188123189 ... 39342926827061468856047302507 (409 digits) 504201578106980562530763299184 ... 34364678167335124247362214481 (503 digits) 305110124747393800923565587415 ... 27995099969296158361330018201 (888 digits) 468185470426936945550027667953 ... 73037342708664543144645856321 (1020 digits) 871013478530378198843208828928 ... 72170748420128396998865227391 (1122 digits) First 30 Iccanobif primes: 2 (1 digit) 3 (1 digit) 5 (1 digit) 31 (2 digits) 43 (2 digits) 773 (3 digits) 7951 (4 digits) 64901 (5 digits) 52057 (5 digits) 393121 (6 digits) 56577108676171 (14 digits) 940647607443258103531 (21 digits) 5237879497657222310489731409575442761 (37 digits) 9026258083384996860449366072142307801963 (40 digits) 19900335674812302969315720344396951060628175943800862267761734431012073266446403 (80 digits) 778411373629674799853537498387 ... 06414225852312097783685331923 (104 digits) 377225859015676041888905465423 ... 42640418929174997072830756131 (137 digits) 757361938948761315956093082097 ... 05343825250767238644714305761 (330 digits) 178903368473328376208382371633 ... 39766460613175300695235035913 (406 digits) 923271631017291153059188123189 ... 39342926827061468856047302507 (409 digits) 504201578106980562530763299184 ... 34364678167335124247362214481 (503 digits) 305110124747393800923565587415 ... 27995099969296158361330018201 (888 digits) 468185470426936945550027667953 ... 73037342708664543144645856321 (1020 digits) 871013478530378198843208828928 ... 72170748420128396998865227391 (1122 digits) First 30 Iccanobif primes: 2 (1 digit) 3 (1 digit) 5 (1 digit) 31 (2 digits) 43 (2 digits) 773 (3 digits) 7951 (4 digits) 64901 (5 digits) 52057 (5 digits) 393121 (6 digits) 56577108676171 (14 digits) 940647607443258103531 (21 digits) 5237879497657222310489731409575442761 (37 digits) 9026258083384996860449366072142307801963 (40 digits) 19900335674812302969315720344396951060628175943800862267761734431012073266446403 (80 digits) 778411373629674799853537498387 ... 06414225852312097783685331923 (104 digits) 377225859015676041888905465423 ... 42640418929174997072830756131 (137 digits) 757361938948761315956093082097 ... 05343825250767238644714305761 (330 digits) 178903368473328376208382371633 ... 39766460613175300695235035913 (406 digits) 923271631017291153059188123189 ... 39342926827061468856047302507 (409 digits) 504201578106980562530763299184 ... 34364678167335124247362214481 (503 digits) 305110124747393800923565587415 ... 27995099969296158361330018201 (888 digits) 468185470426936945550027667953 ... 73037342708664543144645856321 (1020 digits) 871013478530378198843208828928 ... 72170748420128396998865227391 (1122 digits) 174516560225437653361964336594 ... 30820185220100243761843652461 (1911 digits) 489893405662883994748316933771 ... 74664296802930339234215909399 (1947 digits) 127469276849582096547381559312 ... 19580690153436989647994940101 (2283 digits) 357468265826587510126602192036 ... 69346589325010735912438195633 (3727 digits) 879871752812976577066489068488 ... 66056251048748727893681871587 (4270 digits) ^C (took too long)
Raku
sub abbr ($_) { (.chars < 41 ?? $_ !! .substr(0,20) ~ '..' ~ .substr(*-20)) ~ " (digits: {.chars})" }
say (++$).fmt('%2d') ~ ': ' ~ .flip.&abbr for (lazy (1,1,*+*…*).hyper.grep: {.flip.is-prime})[^25];
- Output:
1: 2 (digits: 1) 2: 3 (digits: 1) 3: 5 (digits: 1) 4: 31 (digits: 2) 5: 43 (digits: 2) 6: 773 (digits: 3) 7: 7951 (digits: 4) 8: 64901 (digits: 5) 9: 52057 (digits: 5) 10: 393121 (digits: 6) 11: 56577108676171 (digits: 14) 12: 940647607443258103531 (digits: 21) 13: 5237879497657222310489731409575442761 (digits: 37) 14: 9026258083384996860449366072142307801963 (digits: 40) 15: 19900335674812302969..34431012073266446403 (digits: 80) 16: 77841137362967479985..52312097783685331923 (digits: 104) 17: 37722585901567604188..29174997072830756131 (digits: 137) 18: 75736193894876131595..50767238644714305761 (digits: 330) 19: 17890336847332837620..13175300695235035913 (digits: 406) 20: 92327163101729115305..27061468856047302507 (digits: 409) 21: 50420157810698056253..67335124247362214481 (digits: 503) 22: 30511012474739380092..69296158361330018201 (digits: 888) 23: 46818547042693694555..08664543144645856321 (digits: 1020) 24: 87101347853037819884..20128396998865227391 (digits: 1122) 25: 17451656022543765336..20100243761843652461 (digits: 1911) 26: 48989340566288399474..02930339234215909399 (digits: 1947) 27: 12746927684958209654..53436989647994940101 (digits: 2283) 28: 35746826582658751012..25010735912438195633 (digits: 3727) 29: 87987175281297657706..48748727893681871587 (digits: 4270) 30: 81807376367113798363..13687506007959668569 (digits: 10527)
Wren
import "./gmp" for Mpz
import "./fmt" for Fmt
var fib = Mpz.new()
var p = Mpz.new()
var prev = Mpz.zero
var curr = Mpz.one
var count = 0
System.print("First 30 Iccanobif primes:")
while (count < 30) {
fib.add(curr, prev)
var fs = fib.toString
p.setStr(fs[-1..0])
if (p.probPrime(15) > 0) {
count = count + 1
var pc = p.toString.count
Fmt.print("$2d: $20a ($d digits)", count, p, pc)
}
prev.set(curr)
curr.set(fib)
}
- Output:
First 27 Iccanobif primes: 1: 2 (1 digits) 2: 3 (1 digits) 3: 5 (1 digits) 4: 31 (2 digits) 5: 43 (2 digits) 6: 773 (3 digits) 7: 7951 (4 digits) 8: 64901 (5 digits) 9: 52057 (5 digits) 10: 393121 (6 digits) 11: 56577108676171 (14 digits) 12: 940647607443258103531 (21 digits) 13: 5237879497657222310489731409575442761 (37 digits) 14: 9026258083384996860449366072142307801963 (40 digits) 15: 19900335674812302969...34431012073266446403 (80 digits) 16: 77841137362967479985...52312097783685331923 (104 digits) 17: 37722585901567604188...29174997072830756131 (137 digits) 18: 75736193894876131595...50767238644714305761 (330 digits) 19: 17890336847332837620...13175300695235035913 (406 digits) 20: 92327163101729115305...27061468856047302507 (409 digits) 21: 50420157810698056253...67335124247362214481 (503 digits) 22: 30511012474739380092...69296158361330018201 (888 digits) 23: 46818547042693694555...08664543144645856321 (1020 digits) 24: 87101347853037819884...20128396998865227391 (1122 digits) 25: 17451656022543765336...20100243761843652461 (1911 digits) 26: 48989340566288399474...02930339234215909399 (1947 digits) 27: 12746927684958209654...53436989647994940101 (2283 digits) 28: 35746826582658751012...25010735912438195633 (3727 digits) 29: 87987175281297657706...48748727893681871587 (4270 digits) 30: 81807376367113798363...13687506007959668569 (10527 digits)