A243997 a(n) = phi(sigma(n) - phi(n) - d(n)), where phi(n) is the Euler totient function, sigma(n) the sum of divisors of n and d(n) the number of divisors of n.

1, 0, 0, 1, 0, 2, 0, 6, 2, 4, 0, 6, 0, 6, 4, 6, 0, 18, 0, 12, 8, 10, 0, 20, 4, 12, 6, 18, 0, 24, 0, 40, 8, 16, 8, 24, 0, 18, 12, 20, 0, 36, 0, 28, 16, 22, 0, 42, 4, 66, 12, 32, 0, 46, 12, 40, 16, 28, 0, 48, 0, 30, 30, 40, 16, 56, 0, 40, 16, 48, 0, 104, 0, 36

Offset

1,6

Comments

Subset of A243995.

a(p)=0 if p is prime.

Links

Paolo P. Lava, Table of n, a(n) for n = 1..1000

Example

sigma(72) = 195, phi(72) = 24, d(72) = 12 and phi(195 - 24 - 12) = 104.

Maple

with(numtheory): P:=proc(q) local n;
for n from 1 to q do print(phi(sigma(n)-phi(n)-tau(n)));
od; end: P(100);

Crossrefs

Cf. A000005, A000010, A000203, A243995.

Sequence in context: A322093 A277681 A140876 * A036044 A335790 A078991

Adjacent sequences: A243994 A243995 A243996 * A243998 A243999 A244000

Keyword

nonn,easy

Author

Paolo P. Lava, Jun 19 2014

Status

approved