A001876 Number of divisors of n of form 5k+1; a(0)=0.

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

Offset

0,7

Links

T. D. Noe, Table of n, a(n) for n = 0..10000

Formula

G.f.: Sum_{n>=0} x^(5n+1)/(1-x^(5n+1)).

G.f.: Sum_{n>=1} x^n/(1-x^(5*n)). - Joerg Arndt, Jan 30 2011

Mathematica

CoefficientList[ Series[ Together[ Sum[ x^n/(1 - x^(5n)), {n, 110}]], {x, 0, 110}], x] (* Robert G. Wilson v, Jan 31 2011 *)

Prog

(PARI) a(n) = if(n==0, 0, sumdiv(n, d, (d % 5) == 1)); \\ Michel Marcus, Feb 25 2021

Crossrefs

For numbers of divisors of n of form 5k+i (i=1, 2, 3, 4) see: this sequence, A001877, A001878, A001899.

Sequence in context: A215870 A097587 A001179 * A033182 A053797 A254011

Adjacent sequences: A001873 A001874 A001875 * A001877 A001878 A001879

Keyword

nonn

Author

N. J. A. Sloane

Status

approved