A363850 Number of divisors of 7*n-3 of form 7*k+1.

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

Offset: 1

Author

Seiichi Manyama, Jun 24 2023

Keywords

• nonn

Comments

Also number of divisors of 7*n-3 of form 7*k+4.

Crossrefs

Cf. A279061, A363806.

Programs

Mathematica

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

PARI

a(n) = sumdiv(7*n-3, d, d%7==1);

Formula

a(n) = A279061(7*n-3) = A363806(7*n-3).

G.f.: Sum_{k>0} x^(4*k-3)/(1 - x^(7*k-6)).

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