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 A135694 #17 Dec 12 2023 08:43:51
%S A135694 1,-1,-1,-1,0,2,1,-1,-1,-1,0,2,1,-1,-1,-1,0,2,1,-1,-1,-1,0,2,1,-1,-1,
%T A135694 -1,0,2,1,-1,-1,-1,0,2,1,-1,-1,-1,0,2,1,-1,-1,-1,0,2,1,-1,-1,-1,0,2,1,
%U A135694 -1,-1,-1,0,2,1,-1,-1,-1,0,2,1,-1,-1,-1,0,2,1,-1,-1,-1,0,2,1,-1,-1,-1,0,2
%N A135694 Period 6: repeat [1, -1, -1, -1, 0, 2].
%H A135694 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,-1,0,-1).
%F A135694 From _R. J. Mathar_, Mar 31 2008: (Start)
%F A135694 a(n) = a(n-6) for n>5. a(n) = -a(n-2) - a(n-4) for n>3.
%F A135694 a(n) = (A119910(n+3) - A049347(n+1))/2 for n>0.
%F A135694 G.f.: (1-x-2*x^3)/((x^2-x+1)*(x^2+x+1)). (End)
%F A135694 a(n) = (3*cos(n*Pi/3) - 8*sqrt(3)*cos(n*Pi/6)^3*sin(n*Pi/6))/3. - _Wesley Ivan Hurt_, Jun 22 2016
%p A135694 A135694 := proc(n) op((n mod 6)+1,[1,-1,-1,-1,0,2]) ; end: seq(A135694(n), n=0..150) ; # _R. J. Mathar_, Feb 07 2009
%t A135694 PadRight[{}, 100, {1, -1, -1, -1, 0, 2}] (* _Wesley Ivan Hurt_, Jun 22 2016 *)
%o A135694 (Magma) &cat [[1, -1, -1, -1, 0, 2]^^20]; // _Wesley Ivan Hurt_, Jun 22 2016
%Y A135694 Cf. A000079, A049347, A119910, A135575.
%K A135694 sign,easy
%O A135694 0,6
%A A135694 _Paul Curtz_, Feb 24 2008
%E A135694 More periods from _R. J. Mathar_, Feb 07 2009