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 A318884 #11 Feb 16 2025 08:33:56 %S A318884 2,2,3,2,5,3,7,2,3,5,11,3,13,7,7,2,17,3,19,5,9,11,23,3,5,13,3,7,29,7, %T A318884 31,2,15,17,17,3,37,19,17,5,41,9,43,11,7,23,47,3,7,5,23,13,53,3,17,7, %U A318884 25,29,59,7,61,31,9,2,31,15,67,17,31,17,71,3,73,37,7,19,31,17,79,5,3,41,83,9,41,43,39,11,89 %N A318884 a(n) is the sum of absolute values of the coefficients in the n-th cyclotomic polynomial. %C A318884 Differs from A051664 in the positions given by A013590, thus for the first time at n=105, where a(105) = 35, while A051664(105) = 33 as the 105th cyclotomic polynomial is the first one that has a coefficient other than 1, 0, or -1. %H A318884 Antti Karttunen, <a href="/A318884/b318884.txt">Table of n, a(n) for n = 1..65537</a> %H A318884 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CyclotomicPolynomial.html">Cyclotomic Polynomial</a> %H A318884 Wikipedia, <a href="https://en.wikipedia.org/wiki/Cyclotomic_polynomial">Cyclotomic polynomial</a> %t A318884 Array[Total@ Abs@ CoefficientList[Cyclotomic[#, x], x] &, 89] (* _Michael De Vlieger_, Sep 10 2018 *) %o A318884 (PARI) A318884(n) = vecsum(apply(abs,Vec(polcyclo(n)))); \\ _Antti Karttunen_, Sep 10 2018 %Y A318884 Cf. A013590, A013595, A051258, A051664, A318886. %K A318884 nonn %O A318884 1,1 %A A318884 _Antti Karttunen_, Sep 10 2018