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 A020521 #13 Jul 15 2016 11:27:57
%S A020521 13,8191,22369621,78536544841,300239975158033,1190112520884487201,
%T A020521 4797324681010433232961,19495118728903626376364161,
%U A020521 79538861190790864407636279553,325153619321163373997995856232961,1330527338889299954891005307651097601
%N A020521 13th cyclotomic polynomial evaluated at powers of 2.
%H A020521 Quynh Nguyen, Jean Pedersen, and Hien T. Vu, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL19/Pedersen/pedersen2.html">New Integer Sequences Arising From 3-Period Folding Numbers</a>, Vol. 19 (2016), Article 16.3.1. Cites this sequence.
%F A020521 a(n) = A060887(A000079(n)). - _Michel Marcus_, Apr 06 2016
%F A020521 G.f.: Sum_{k=0..12} 1/(1-2^k*x). - _Benedict W. J. Irwin_, Jul 15 2016
%p A020521 with(numtheory,cyclotomic):seq(cyclotomic(13,2^i),i=0..24);
%t A020521 Table[Cyclotomic[13,2^n],{n,0,24}] (* _Benedict W. J. Irwin_, Jul 15 2016 *)
%o A020521 (PARI) a(n) = polcyclo(13, 2^n); \\ _Michel Marcus_, Apr 06 2016
%Y A020521 Cf. A000079, A060887.
%K A020521 nonn
%O A020521 0,1
%A A020521 _Simon Plouffe_