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 A131974 #30 Dec 12 2023 08:53:10
%S A131974 1,2,3,4,-5,-4,-3,-2,1,2,3,4,-5,-4,-3,-2,1,2,3,4,-5,-4,-3,-2,1,2,3,4,
%T A131974 -5,-4,-3,-2,1,2,3,4,-5,-4,-3,-2,1,2,3,4,-5,-4,-3,-2,1,2,3,4,-5,-4,-3,
%U A131974 -2,1,2,3,4,-5,-4,-3,-2,1,2,3,4,-5,-4,-3,-2
%N A131974 Period 8: repeat [1, 2, 3, 4, -5, -4, -3, -2].
%H A131974 <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,0,0,1).
%F A131974 G.f.: (1 + 2*x + 3*x^2 + 4*x^3 - 5*x^4 - 4*x^5 - 3*x^6 - 2*x^7)/(1-x^8). - _Wesley Ivan Hurt_, Aug 31 2019
%F A131974 a(n) = a(n-8). - _Wesley Ivan Hurt_, Nov 28 2021
%t A131974 CoefficientList[Series[(1 + 2*x + 3*x^2 + 4*x^3 - 5*x^4 - 4*x^5 - 3*x^6 - 2*x^7)/(1 - x^8), {x, 0, 80}], x] (* _Wesley Ivan Hurt_, Aug 31 2019 *)
%t A131974 PadRight[{},120,{1,2,3,4,-5,-4,-3,-2}] (* _Harvey P. Dale_, Aug 10 2022 *)
%o A131974 (PARI) a(n)=[1,2,3,4,-5,-4,-3,-2][n%8+1] \\ _Charles R Greathouse IV_, Jun 02 2011
%K A131974 sign,easy,less
%O A131974 0,2
%A A131974 _Paul Curtz_, Oct 06 2007