Primes which contain only one odd digit: Difference between revisions

=={{header|FreeBASIC}}==

<lang freebasic>

#include "isprime.bas"

function b(j as uinteger, n as uinteger) as uinteger

'auxiliary function for evendig below

dim as uinteger m = int(log(n-1)/log(5))

return int((n-1-5^m)/5^j)

end function

function evendig(n as uinteger) as uinteger

'produces the integers with only even digits

dim as uinteger m = int(log(n-1)/log(5)), a

a = ((2*b(m, n)) mod 8 + 2)*10^m

if n<=1 or m=0 then return a

for j as uinteger = 0 to m-1

a += ((2*b(j, n)) mod 10)*10^j

next j

return a

end function

dim as uinteger n=1, count = 0, p=1

while p<1000000

p = 1 + evendig(n) 'if it's a prime the odd digit must be the last one

if isprime(p) then

count += 1

if p<1000 then print p

end if

n+=1

wend

print "There are ";count;" such primes below one million."</lang>