A363856 Number of divisors of 7*n-4 of form 7*k+6.

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

Offset: 1

Author

Seiichi Manyama, Jun 24 2023

Keywords

• nonn

Comments

Also number of divisors of 7*n-4 of form 7*k+4.

Crossrefs

Cf. A361691, A363854, A363855, A363857, A363858.

Cf. A363806, A363808.

Programs

Mathematica

a[n_] := DivisorSum[7*n - 4, 1 &, Mod[#, 7] == 6 &]; Array[a, 100] (* Amiram Eldar, Jun 25 2023 *)

PARI

a(n) = sumdiv(7*n-4, d, d%7==6);

Formula

a(n) = A363806(7*n-4) = A363808(7*n-4).

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

G.f.: Sum_{k>0} x^(6*k-2)/(1 - x^(7*k-3)).