This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A035177 #14 Jul 08 2025 21:31:17
%S A035177 1,0,0,1,0,0,2,0,1,0,2,0,1,0,0,1,2,0,2,0,0,0,0,0,1,0,0,2,2,0,2,0,0,0,
%T A035177 0,1,0,0,0,0,0,0,0,2,0,0,2,0,3,0,0,1,2,0,0,0,0,0,2,0,2,0,2,1,0,0,2,2,
%U A035177 0,0,2,0,0,0,0,2,4,0,0,0,1
%N A035177 Coefficients in expansion of Dirichlet series Product_p (1-(Kronecker(m,p)+1)*p^(-s)+Kronecker(m,p)*p^(-2s))^(-1) for m = -13.
%H A035177 Amiram Eldar, <a href="/A035177/b035177.txt">Table of n, a(n) for n = 1..10000</a>
%F A035177 From _Amiram Eldar_, Nov 17 2023 (Start)
%F A035177 a(n) = Sum_{d|n} Kronecker(-13, d).
%F A035177 Multiplicative with a(13^e) = 1, a(p^e) = (1+(-1)^e)/2 if Kronecker(-13, p) = -1, and a(p^e) = e+1 if Kronecker(-13, p) = 1 (p is in A296926).
%F A035177 Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = 2*Pi/(3*sqrt(13)) = 0.5808806... . (End)
%t A035177 a[n_] := DivisorSum[n, KroneckerSymbol[-13, #] &]; Array[a, 100] (* _Amiram Eldar_, Nov 17 2023 *)
%o A035177 (PARI) my(m = -13); direuler(p=2,101,1/(1-(kronecker(m,p)*(X-X^2))-X))
%o A035177 (PARI) a(n) = sumdiv(n, d, kronecker(-13, d)); \\ _Amiram Eldar_, Nov 17 2023
%Y A035177 Cf. A296926.
%K A035177 nonn,easy,mult
%O A035177 1,7
%A A035177 _N. J. A. Sloane_