A363858 - OEIS

A363858

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

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

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OFFSET

1,12

LINKS

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

FORMULA

a(n) = A363808(7*n-6).

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

MATHEMATICA

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

PROG

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