A363891 Sum of divisors of 3*n-2 of form 3*k+2.

0, 2, 0, 7, 0, 10, 0, 13, 5, 16, 0, 19, 0, 35, 0, 25, 0, 28, 16, 31, 0, 42, 0, 56, 0, 40, 0, 43, 22, 65, 0, 49, 0, 77, 0, 55, 0, 80, 28, 61, 11, 64, 0, 98, 0, 95, 0, 73, 34, 76, 0, 104, 0, 147, 0, 85, 0, 88, 40, 91, 0, 125, 28, 140, 0, 114, 0, 103, 46, 140, 0, 109, 0, 192, 0, 115, 0

Offset: 1

Author

Seiichi Manyama, Jun 26 2023

Keywords

• nonn

Links

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

Crossrefs

Cf. A363514, A363889, A363890.

Cf. A078182, A359239.

Programs

Mathematica

a[n_] := DivisorSum[3*n - 2, # &, Mod[#, 3] == 2 &]; Array[a, 100] (* Amiram Eldar, Jun 26 2023 *)

PARI

a(n) = sumdiv(3*n-2, d, (d%3==2)*d);

Formula

a(n) = A078182(3*n-2).

G.f.: Sum_{k>0} (3*k-1) * x^(2*k)/(1 - x^(3*k-1)).