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 A014027 #34 Dec 14 2023 05:51:42
%S A014027 1,0,0,1,0,0,0,0,0,-1,0,0,-1,0,0,0,0,0,1,0,0,1,0,0,0,0,0,-1,0,0,-1,0,
%T A014027 0,0,0,0,1,0,0,1,0,0,0,0,0,-1,0,0,-1,0,0,0,0,0,1,0,0,1,0,0,0,0,0,-1,0,
%U A014027 0,-1,0,0,0,0,0,1,0,0,1,0,0,0,0,0
%N A014027 Inverse of 18th cyclotomic polynomial.
%C A014027 Periodic with period length 18. - _Ray Chandler_, Apr 03 2017
%H A014027 Vincenzo Librandi, <a href="/A014027/b014027.txt">Table of n, a(n) for n = 0..1000</a>
%H A014027 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (0, 0, 1, 0, 0, -1).
%H A014027 <a href="/index/Pol#poly_cyclo_inv">Index to sequences related to inverse of cyclotomic polynomials</a>
%F A014027 G.f.: 1 / ( 1-x^3+x^6 ). - _R. J. Mathar_, Mar 11 2011
%p A014027 with(numtheory,cyclotomic); c := n->series(1/cyclotomic(n,x),x,80);
%t A014027 CoefficientList[Series[1/Cyclotomic[18, x], {x, 0, 100}], x] (* _Vincenzo Librandi_, Apr 03 2014 *)
%t A014027 LinearRecurrence[{0, 0, 1, 0, 0, -1},{1, 0, 0, 1, 0, 0},81] (* _Ray Chandler_, Sep 15 2015 *)
%o A014027 (PARI) Vec(1/polcyclo(18)+O(x^99)) \\ _Charles R Greathouse IV_, Mar 24 2014
%o A014027 (Magma) &cat[[1,0,0,1,0,0,0,0,0,-1,0,0,-1,0,0,0,0,0]: n in [0..8]]; // _Vincenzo Librandi_, Apr 03 2014
%K A014027 sign,easy
%O A014027 0,1
%A A014027 _Simon Plouffe_