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

1,5

Comments

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

Links

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

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)).

Mathematica

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

Prog

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

Crossrefs

Cf. A279061, A363806.

Sequence in context: A327499 A353693 A327857 * A227481 A143654 A170981

Adjacent sequences: A363847 A363848 A363849 * A363851 A363852 A363853

Keyword

nonn

Author

Seiichi Manyama, Jun 24 2023

Status

approved