A326047 a(n) = gcd(n-A050449(n), n-A050452(n)), where A050449 and A050452 give the sum of divisors of the form 4k+1 and of the form 4k+3, respectively.

1, 1, 2, 1, 1, 1, 6, 1, 1, 2, 10, 1, 1, 1, 3, 1, 1, 1, 18, 2, 1, 1, 22, 1, 1, 2, 1, 3, 1, 12, 30, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 4, 42, 1, 3, 1, 46, 1, 1, 1, 3, 2, 1, 4, 1, 1, 1, 2, 58, 6, 1, 1, 2, 1, 1, 4, 66, 2, 1, 4, 70, 1, 1, 2, 2, 3, 1, 4, 78, 2, 1, 2, 82, 2, 1, 1, 3, 1, 1, 6, 7, 1, 1, 1, 1, 1, 1, 1, 14, 1, 1, 12, 102, 2, 9

Offset: 1

Author

Antti Karttunen, Jun 04 2019

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..65537

Crossrefs

Cf. A050449, A050452, A326048, A326049, A326052

Programs

PARI

A050449(n) = sumdiv(n, d, d*((d % 4) == 1)); \\ From A050449
A326049(n) = (n-A050449(n));
A050452(n) = sumdiv(n, d, d*(3==(d % 4)));
A326052(n) = (n-A050452(n));
A326047(n) = gcd(A326049(n), A326052(n));

Formula

a(n) = gcd(A326049(n), A326052(n)) = gcd(n-A050449(n), n-A050452(n)).

a(2n-1) = A326048(2n-1) for all n.