A137413 - OEIS

A137413

a(n) = the number of positive integers that are <= n and are coprime to (the sum of the distinct prime divisors of n).

1, 1, 2, 2, 4, 5, 6, 4, 6, 9, 10, 10, 12, 10, 8, 8, 16, 15, 18, 18, 9, 21, 22, 20, 20, 14, 18, 19, 28, 12, 30, 16, 15, 33, 12, 29, 36, 22, 20, 35, 40, 14, 42, 41, 23, 37, 46, 39, 42, 43, 21, 28, 52, 44, 28, 38, 26, 57, 58, 24, 60, 38, 26, 32, 22, 33, 66, 65, 32, 30, 70, 58, 72, 46

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OFFSET

1,3

LINKS

Table of n, a(n) for n=1..74.

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

Cf.A008472.

Sequence in context:A126870 A364049 A368866*A010848 A133937 A181523

Adjacent sequences:A137410 A137411 A137412*A137414 A137415 A137416

KEYWORD

nonn

AUTHOR

Leroy Quet,Apr 15 2008

EXTENSIONS

More terms fromHagen von Eitzen,Jun 16 2009

STATUS

approved