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 A384765 #57 Jul 23 2025 16:09:37
%S A384765 -2,0,1,0,1,3,1,0,1,5,1,3,1,7,1,0,1,3,1,5,1,11,1,3,1,13,1,7,1,1,1,0,1,
%T A384765 17,1,3,1,19,1,5,1,1,1,11,1,23,1,3,1,5,1,13,1,3,1,7,1,29,1,1,1,31,1,0,
%U A384765 1,1,1,17,1,1,1,3,1,37,1,19,1,1,1,5,1
%N A384765 a(n) is the rad(n)-th cyclotomic polynomial evaluated at x = -1.
%C A384765 The polynomials from A374385 (for n > 1), evaluated at x = -1.
%F A384765 a(n) = A020513(A007947(n)). - _Andrei Zabolotskii_, Jul 21 2025
%t A384765 nn = 81; A023900[n_] := Total[Divisors[n]*MoebiusMu[Divisors[n]]]; tt = Table[Simplify@Factor[Sum[A023900[GCD[n, k]]*x^k, {k, 1, n}]/(1 - x^n)], {n, 1, nn}];
%t A384765 Denominator[tt] /. {x -> -1}
%Y A384765 Cf. A020513, A020500, A374412, A374385, A191898, A023900, A007947, A000079.
%K A384765 sign
%O A384765 1,1
%A A384765 _Mats Granvik_, Jun 09 2025