A363855 Number of divisors of 7*n-3 of form 7*k+6.

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

Offset

1,9

Comments

Also number of divisors of 7*n-3 of form 7*k+3.

Links

Table of n, a(n) for n=1..100.

Formula

a(n) = A363805(7*n-3) = A363808(7*n-3).

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

G.f.: Sum_{k>0} x^(6*k-3)/(1 - x^(7*k-4)).

Mathematica

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

Prog

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

Crossrefs

Cf. A361691, A363854, A363856, A363857, A363858.

Cf. A363805, A363808.

Sequence in context: A215020 A103612 A083913 * A023670 A284394 A188170

Adjacent sequences: A363852 A363853 A363854 * A363856 A363857 A363858

Keyword

nonn

Author

Seiichi Manyama, Jun 24 2023

Status

approved