A359326 Number of divisors of 6*n-4 of form 6*k+5.

0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 1, 0, 1, 0, 1, 0, 0, 2, 1, 0, 0, 0, 2, 0, 0, 0, 1, 2, 1, 0, 1, 0, 1, 0, 1, 0, 0, 2, 1, 1, 0, 0, 2, 0, 1, 0, 1, 2, 0, 0, 2, 0, 1, 0, 1, 0, 0, 2, 1, 0, 1, 2, 2, 0, 0, 0, 1, 2, 0, 0, 1, 0, 2, 0, 1, 0, 1, 2, 2, 0, 0, 0, 2, 2, 0, 0, 1, 2, 0

Offset: 1

Author

Seiichi Manyama, Dec 25 2022

Keywords

• nonn
• easy

Links

• Seiichi Manyama, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A319995, A359305, A359324, A359325, A359327.

Programs

Mathematica

a[n_] := DivisorSum[6*n-4, 1 &, Mod[#, 6] == 5 &]; Array[a, 100] (* Amiram Eldar, Aug 14 2023 *)

PARI

a(n) = sumdiv(6*n-4, d, d%6==5);

PARI

my(N=100, x='x+O('x^N)); concat([0, 0, 0], Vec(sum(k=1, N, x^(4*k)/(1-x^(6*k-1)))))

PARI

my(N=100, x='x+O('x^N)); concat([0, 0, 0], Vec(sum(k=1, N, x^(5*k-1)/(1-x^(6*k-2)))))

Formula

a(n) = A319995(6*n-4).

G.f.: Sum_{k>0} x^(4*k)/(1 - x^(6*k-1)).

G.f.: Sum_{k>0} x^(5*k-1)/(1 - x^(6*k-2)).