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 A020508 #14 Sep 09 2017 03:55:49
%S A020508 -9,-10,-8,73,82,5905,91,478297,6562,530713,7381,3138105961,6481,
%T A020508 254186582833,597871,47763361,43046722,1667718169966657,532171,
%U A020508 135085171767299209,42521761,313380653041,3922632451
%N A020508 Cyclotomic polynomials at x=-9.
%H A020508 <a href="/index/Cy#CyclotomicPolynomialsValuesAtX">Index entries for cyclotomic polynomials, values at X</a>
%p A020508 with(numtheory,cyclotomic); f := n->subs(x=-9,cyclotomic(n,x)); seq(f(i),i=0..64);
%t A020508 Join[{-9}, Table[Cyclotomic[n, -9], {n, 1, 22}]] (* _Jean-François Alcover_, Sep 09 2017 *)
%K A020508 sign
%O A020508 0,1
%A A020508 _Simon Plouffe_