A363880 Number of divisors of 7*n-6 of form 7*k+3.

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

Offset: 1

Author

Seiichi Manyama, Jun 25 2023

Keywords

• nonn

Comments

Also number of divisors of 7*n-6 of form 7*k+5.

Crossrefs

Cf. A363805, A363807.

Programs

Mathematica

a[n_] := DivisorSum[7*n - 6, 1 &, Mod[#, 7] == 3 &]; Array[a, 100] (* Amiram Eldar, Jun 25 2023 *)

PARI

a(n) = sumdiv(7*n-6, d, d%7==3);

Formula

a(n) = A363805(7*n-6) = A363807(7*n-6).

G.f.: Sum_{k>0} x^(5*k-2)/(1 - x^(7*k-4)).

G.f.: Sum_{k>0} x^(3*k)/(1 - x^(7*k-2)).