A359288 Number of divisors of 5*n-1 of form 5*k+3.

0, 1, 0, 0, 2, 0, 0, 2, 0, 0, 2, 0, 1, 2, 0, 0, 2, 0, 0, 2, 2, 0, 2, 0, 0, 2, 0, 0, 4, 0, 0, 2, 0, 1, 2, 0, 2, 2, 0, 0, 2, 0, 0, 2, 2, 0, 4, 0, 0, 2, 0, 0, 4, 0, 0, 2, 0, 0, 2, 2, 2, 2, 0, 0, 3, 0, 0, 2, 2, 0, 2, 0, 2, 2, 0, 0, 4, 0, 0, 2, 0, 0, 4, 0, 2, 4, 0, 0, 2, 0

Offset

1,5

Links

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

Formula

a(n) = A001878(5*n-1).

G.f.: Sum_{k>0} x^(3*k-1)/(1 - x^(5*k-2)).

Mathematica

a[n_] := DivisorSum[5*n-1, 1 &, Mod[#, 5] == 3 &]; Array[a, 100] (* Amiram Eldar, Aug 16 2023 *)

Prog

(PARI) a(n) = sumdiv(5*n-1, d, d%5==3);
(PARI) my(N=100, x='x+O('x^N)); concat(0, Vec(sum(k=1, N, x^(3*k-1)/(1-x^(5*k-2)))))

Crossrefs

Cf. A001878.

Cf. A359233, A359287.

Cf. A359236, A359244, A359270.

Sequence in context: A341792 A341793 A341773 * A096142 A216921 A344982

Adjacent sequences: A359285 A359286 A359287 * A359289 A359290 A359291

Keyword

nonn,easy

Author

Seiichi Manyama, Dec 24 2022

Status

approved