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 A020506 #19 Feb 26 2024 10:26:34
%S A020506 -7,-8,-6,43,50,2101,57,102943,2402,117307,2801,247165843,2353,
%T A020506 12111126301,137257,6568801,5764802,29078814248401,117993,
%U A020506 1424861898171643,5649505,15772610449,329554457,3421093417510114543,5762401,79787519018560501,16148168401,1628413557556843
%N A020506 Cyclotomic polynomials at x = -7.
%C A020506 Sequence has a(0) = x; see comments in A020501.
%H A020506 Paolo Xausa, <a href="/A020506/b020506.txt">Table of n, a(n) for n = 0..1000</a>
%H A020506 <a href="/index/Cy#CyclotomicPolynomialsValuesAtX">Index entries for cyclotomic polynomials, values at X</a>
%p A020506 with(numtheory,cyclotomic); f := n->subs(x=-7,cyclotomic(n,x)); seq(f(i),i=0..64);
%t A020506 Join[{-7}, Cyclotomic[Range[50], -7]] (* _Paolo Xausa_, Feb 26 2024 *)
%o A020506 (PARI) a(n) = if(n==0, -7, polcyclo(n, -7)); \\ _Michel Marcus_, Dec 17 2017
%K A020506 sign
%O A020506 0,1
%A A020506 _Simon Plouffe_
%E A020506 More terms from _Michel Marcus_, Dec 17 2017