A363880 Number of divisors of 7*n-6 of form 7*k+3.

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

Offset

1,18

Comments

Also number of divisors of 7*n-6 of form 7*k+5.

Links

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

Formula

a(n) = A363805(7*n-6) = A363807(7*n-6).

G.f.: Sum_{k>0} x^(5*k-2)/(1 - x^(7*k-4)).

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

Mathematica

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

Prog

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

Crossrefs

Cf. A363805, A363807.

Sequence in context: A005890 A104515 A337923 * A324874 A324862 A324864

Adjacent sequences: A363877 A363878 A363879 * A363881 A363882 A363883

Keyword

nonn

Author

Seiichi Manyama, Jun 25 2023

Status

approved