A363887 Number of divisors of 7*n-5 of form 7*k+3.

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

Offset

1,5

Links

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

Formula

a(n) = A363805(7*n-5).

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

Mathematica

a[n_] := DivisorSum[7*n - 5, 1 &, Mod[#, 7] == 3 &]; Array[a, 100] (* Amiram Eldar, Jun 26 2023 *)

Prog

(PARI) a(n) = sumdiv(7*n-5, d, d%7==3);

Crossrefs

Cf. A363852, A363857, A363888.

Cf. A363805.

Sequence in context: A095808 A281453 A079807 * A341776 A116373 A341777

Adjacent sequences: A363884 A363885 A363886 * A363888 A363889 A363890

Keyword

nonn

Author

Seiichi Manyama, Jun 26 2023

Status

approved