A035169 Coefficients in expansion of Dirichlet series Product_p (1-(Kronecker(m,p)+1)*p^(-s)+Kronecker(m,p)*p^(-2s))^(-1) for m = -21.

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

Offset

1,5

Links

G. C. Greubel, Table of n, a(n) for n = 1..10000

Formula

From Amiram Eldar, Nov 17 2023: (Start)

a(n) = Sum_{d|n} Kronecker(-21, d).

Multiplicative with a(p^e) = 1 if Kronecker(-17, p) = 0 (p = 3 or 7), a(p^e) = (1+(-1)^e)/2 if Kronecker(-17, p) = -1, and a(p^e) = e+1 if Kronecker(-17, p) = 1.

Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = 4*Pi/(3*sqrt(21)) = 0.914068... . (End)

Mathematica

a[n_] := If[n < 0, 0, DivisorSum[n, KroneckerSymbol[-21, #] &]]; Table[a[n], {n, 1, 100}] (* G. C. Greubel, Jul 17 2018 *)

Prog

(PARI) my(m = -21); direuler(p=2, 101, 1/(1-(kronecker(m, p)*(X-X^2))-X))
(PARI) a(n) = sumdiv(n, d, kronecker(-21, d)); \\ Amiram Eldar, Nov 17 2023

Crossrefs

Sequence in context: A324852 A363854 A353967 * A340728 A275851 A067432

Adjacent sequences: A035166 A035167 A035168 * A035170 A035171 A035172

Keyword

nonn,easy,mult

Author

N. J. A. Sloane

Status

approved