OFFSET
1,3
EXAMPLE
The distinct primes dividing 21 are 3 and 7. 3+7 = 10. The positive integers that are <= 21 and are coprime to 10 are 1,3,7,9,11,13,17,19,21. There are 9 of these; so a(21) = 9.
PROG
(PARI) a(n) = local(t=if(n==1, [], factor(n)~[1, ]), s=t*vector(#t, x, 1)~, ct=0, i); for(i=1, n, if(gcd(i, s)==1, ct++)); ct \\ Hagen von Eitzen, Jun 16 2009
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Apr 15 2008
EXTENSIONS
More terms from Hagen von Eitzen, Jun 16 2009
STATUS
approved