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 A020504 #15 Feb 26 2024 10:59:25
%S A020504 -5,-6,-4,21,26,521,31,13021,626,15501,781,8138021,601,203450521,
%T A020504 19531,464881,390626,127156575521,15751,3178914388021,375601,
%U A020504 290639881,12207031,1986821492513021,390001,95336923825001
%N A020504 Cyclotomic polynomials at x=-5.
%H A020504 Paolo Xausa, <a href="/A020504/b020504.txt">Table of n, a(n) for n = 0..1000</a>
%H A020504 <a href="/index/Cy#CyclotomicPolynomialsValuesAtX">Index entries for cyclotomic polynomials, values at X</a>
%p A020504 with(numtheory,cyclotomic); f := n->subs(x=-5,cyclotomic(n,x)); seq(f(i),i=0..64);
%t A020504 Join[{-5}, Cyclotomic[Range[50], -5]] (* _Paolo Xausa_, Feb 26 2024 *)
%K A020504 sign
%O A020504 0,1
%A A020504 _Simon Plouffe_