A363878 Number of divisors of 7*n-4 of form 7*k+2.

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

Offset

1,12

Comments

Also number of divisors of 7*n-4 of form 7*k+5.

Links

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

Formula

a(n) = A363795(7*n-4) = A363807(7*n-4).

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

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

Mathematica

a[n_] := DivisorSum[7*n - 4, 1 &, Mod[#, 7] == 2 &]; Array[a, 100] (* Amiram Eldar, Jun 25 2023 *)

Prog

(PARI) a(n) = sumdiv(7*n-4, d, d%7==2);

Crossrefs

Cf. A363795, A363807.

Sequence in context: A194923 A321103 A358133 * A086372 A342003 A339737

Adjacent sequences: A363875 A363876 A363877 * A363879 A363880 A363881

Keyword

nonn

Author

Seiichi Manyama, Jun 25 2023

Status

approved