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 A156536 #17 Nov 20 2023 00:05:22
%S A156536 7,5,-1,1,-5,-7,-7,-5,1,-1,5,7,7,5,-1,1,-5,-7,-7,-5,1,-1,5,7,7,5,-1,1,
%T A156536 -5,-7,-7,-5,1,-1,5,7,7,5,-1,1,-5,-7,-7,-5,1,-1,5,7,7,5,-1,1,-5,-7,-7,
%U A156536 -5,1,-1,5,7,7,5,-1,1,-5,-7,-7,-5,1,-1,5,7,7,5,-1,1,-5,-7,-7,-5,1,-1,5,7,7,5
%N A156536 Period 12: repeat 7,5,-1,1,-5,-7,-7,-5,1,-1,5,7.
%H A156536 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,-1).
%F A156536 a(n) = A154811(n+6) - A154811(n).
%F A156536 From _R. J. Mathar_, Apr 10 2009: (Start)
%F A156536 a(n) = -a(n-6).
%F A156536 G.f.: -(x-1)*(7*x^4 + 12*x^3 + 11*x^2 + 12*x + 7)/((1+x^2)*(x^4 - x^2 + 1)). (End)
%F A156536 G.f.: (-7*x^5 - 5*x^4 + x^3 - x^2 + 5*x + 7)/(x^6 + 1). - _Chai Wah Wu_, Feb 16 2021
%t A156536 PadRight[{},120,{7,5,-1,1,-5,-7,-7,-5,1,-1,5,7}] (* or *) LinearRecurrence[{0,0,0,0,0,-1},{7,5,-1,1,-5,-7},120] (* _Harvey P. Dale_, Oct 15 2023 *)
%Y A156536 Cf. A154870.
%K A156536 sign,easy
%O A156536 0,1
%A A156536 _Paul Curtz_, Feb 09 2009
%E A156536 Edited by _R. J. Mathar_, Apr 10 2009