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 A020502 #17 Feb 26 2024 10:09:51
%S A020502 -3,-4,-2,7,10,61,13,547,82,703,121,44287,73,398581,1093,8401,6562,
%T A020502 32285041,757,290565367,5905,682969,88573,23535794707,6481,3472494301,
%U A020502 797161,387400807,478297,17157594341221,4561,154418349070987,43046722,4482983209,64570081,374857981681
%N A020502 Cyclotomic polynomials at x=-3.
%H A020502 Paolo Xausa, <a href="/A020502/b020502.txt">Table of n, a(n) for n = 0..1000</a>
%H A020502 <a href="/index/Cy#CyclotomicPolynomialsValuesAtX">Index entries for cyclotomic polynomials, values at X</a>
%p A020502 with(numtheory,cyclotomic); f := n->subs(x=-3,cyclotomic(n,x)); seq(f(i),i=0..64);
%t A020502 Join[{-3}, Cyclotomic[Range[50], -3]] (* _Paolo Xausa_, Feb 26 2024 *)
%o A020502 (PARI) a(n) = if (n, polcyclo(n, -3), -3); \\ _Michel Marcus_, Oct 30 2018
%K A020502 sign
%O A020502 0,1
%A A020502 _Simon Plouffe_
%E A020502 More terms from _Michel Marcus_, Oct 30 2018