A035203 - OEIS

A035203

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

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OFFSET

1,5

COMMENTS

Coefficients of Dedekind zeta function for the quadratic number field of discriminant 21. See A002324 for formula and Maple code. - N. J. A. Sloane, Mar 22 2022

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

FORMULA

Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = 2*log((5+sqrt(21))/2)/sqrt(21) = 0.683807... . - Amiram Eldar, Oct 11 2022

From Amiram Eldar, Nov 19 2023: (Start)

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

Multiplicative with a(p^e) = 1 if Kronecker(21, p) = 0 (p = 3 or 7), a(p^e) = (1+(-1)^e)/2 if Kronecker(21, p) = -1 (p is in A038894), and a(p^e) = e+1 if Kronecker(21, p) = 1 (p is in A038893 \ {3, 7}). (End)

MATHEMATICA

a[n_] := DivisorSum[n, KroneckerSymbol[21, #] &]; Array[a, 100] (* Amiram Eldar, Oct 11 2022 *)

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 19 2023

CROSSREFS

Dedekind zeta functions for imaginary quadratic number fields of discriminants -3, -4, -7, -8, -11, -15, -19, -20 are A002324, A002654, A035182, A002325, A035179, A035175, A035171, A035170, respectively.

Dedekind zeta functions for real quadratic number fields of discriminants 5, 8, 12, 13, 17, 21, 24, 28, 29, 33, 37, 40 are A035187, A035185, A035194, A035195, A035199, A035203, A035188, A035210, A035211, A035215, A035219, A035192, respectively.

Cf. A038893, A038894.

Sequence in context: A343222 A112378 A324832 * A357905 A173920 A230001

Adjacent sequences: A035200 A035201 A035202 * A035204 A035205 A035206

KEYWORD

nonn,easy,mult

AUTHOR

N. J. A. Sloane

STATUS

approved