A363859 Number of divisors of 7*n-1 of form 7*k+2.

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

Offset

1,7

Comments

Also number of divisors of 7*n-1 of form 7*k+3.

Links

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

Formula

a(n) = A363795(7*n-1) = A363805(7*n-1).

G.f.: Sum_{k>0} x^(3*k-2)/(1 - x^(7*k-5)).

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

Mathematica

a[n_] := DivisorSum[7*n - 1, 1 &, Mod[#, 7] == 2 &]; Array[a, 100] (* Amiram Eldar, Jun 25 2023 *)

Prog

(PARI) a(n) = sumdiv(7*n-1, d, d%7==2);

Crossrefs

Cf. A363795, A363805.

Sequence in context: A034178 A317531 A074169 * A328458 A099362 A321378

Adjacent sequences: A363856 A363857 A363858 * A363860 A363861 A363862

Keyword

nonn

Author

Seiichi Manyama, Jun 24 2023

Status

approved