Chowla numbers: Difference between revisions

</pre>

=={{header|FreeBASIC}}==

{{trans|Visual Basic}}

<lang freebasic>

' Chowla_numbers

#include "string.bi"

Dim Shared As Long limite

limite = 10000000

Dim Shared As Boolean c(limite)

Dim As Long count, topenumprimo, a

count = 1

topenumprimo = 100

Dim As Longint p, k, kk, limitenumperfect

limitenumperfect = 35000000

k = 2: kk = 3

Declare Function chowla(Byval n As Longint) As Longint

Declare Sub sieve(Byval limite As Long, c() As Boolean)

Function chowla(Byval n As Longint) As Longint

Dim As Long i, j, r

i = 2

Do While i * i <= n

j = n \ i

If n Mod i = 0 Then

r += i

If i <> j Then r += j

End If

i += 1

Loop

chowla = r

End Function

Sub sieve(Byval limite As Long, c() As Boolean)

Dim As Long i, j

Redim As Boolean c(limite - 1)

i = 3

Do While i * 3 < limite

If Not c(i) Then

If chowla(i) = false Then

j = 3 * i

Do While j < limite

c(j) = true

j += 2 * i

Loop

End If

End If

i += 2

Loop

End Sub

Print "Chowla numbers"

For a = 1 To 37

Print "chowla(" & Trim(Str(a)) & ") = " & Trim(Str(chowla(a)))

Next a

' Si chowla(n) = falso and n > 1 Entonces n es primo

Print: Print "Contando los numeros primos hasta: "

sieve(limite, c())

For a = 3 To limite - 1 Step 2

If Not c(a) Then count += 1

If a = topenumprimo - 1 Then

Print Using "########## hay"; topenumprimo;

Print count

topenumprimo *= 10

End If

Next a

' Si chowla(n) = n - 1 and n > 1 Entonces n es un número perfecto

Print: Print "Buscando numeros perfectos... "

count = 0

Do

p = k * kk : If p > limitenumperfect Then Exit Do

If chowla(p) = p - 1 Then

Print Using "##########,# es un numero perfecto"; p

count += 1

End If

k = kk + 1 : kk += k

Loop

Print: Print "Hay " & count & " numeros perfectos <= " & Format(limitenumperfect, "###############################,#")

Print: Print "Pulsa una tecla para salir"

Sleep

End

</lang>

{{out}}

<pre>

Chowla numbers

chowla(1) = 0

chowla(2) = 0

chowla(3) = 0

chowla(4) = 2

chowla(5) = 0

chowla(6) = 5

chowla(7) = 0

chowla(8) = 6

chowla(9) = 3

chowla(10) = 7

chowla(11) = 0

chowla(12) = 15

chowla(13) = 0

chowla(14) = 9

chowla(15) = 8

chowla(16) = 14

chowla(17) = 0

chowla(18) = 20

chowla(19) = 0

chowla(20) = 21

chowla(21) = 10

chowla(22) = 13

chowla(23) = 0

chowla(24) = 35

chowla(25) = 5

chowla(26) = 15

chowla(27) = 12

chowla(28) = 27

chowla(29) = 0

chowla(30) = 41

chowla(31) = 0

chowla(32) = 30

chowla(33) = 14

chowla(34) = 19

chowla(35) = 12

chowla(36) = 54

chowla(37) = 0

Contando los numeros primos hasta:

100 hay 25

1000 hay 168

10000 hay 1229

100000 hay 9592

1000000 hay 78498

10000000 hay 664579

Buscando numeros perfectos...

6 es un numero perfecto

28 es un numero perfecto

496 es un numero perfecto

8,128 es un numero perfecto

33,550,336 es un numero perfecto

Hay 5 numeros perfectos <= 35.000.000

Pulsa una tecla para salir