A363860 Number of divisors of 7*n-1 of form 7*k+4.

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

Offset

1,19

Comments

Also number of divisors of 7*n-1 of form 7*k+5.

Links

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

Formula

a(n) = A363806(7*n-1) = A363807(7*n-1).

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

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

Mathematica

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

Prog

(PARI) a(n) = sumdiv(7*n-1, d, d%7==4);

Crossrefs

Cf. A363806, A363807.

Sequence in context: A167688 A083914 A083891 * A087623 A265260 A363888

Adjacent sequences: A363857 A363858 A363859 * A363861 A363862 A363863

Keyword

nonn

Author

Seiichi Manyama, Jun 24 2023

Status

approved