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 A131201 #10 May 27 2021 14:12:51 %S A131201 0,1,2,5,2,9,0,9,8,5,8,1,0,-1,-2,-5,-2,-9,0,-9,-8,-5,-8,-1,0,1,2,5,2, %T A131201 9,0,9,8,5,8,1,0,-1,-2,-5,-2,-9,0,-9,-8,-5,-8,-1,0,1,2,5,2,9,0,9,8,5, %U A131201 8,1,0,-1,-2,-5,-2,-9,0,-9,-8,-5,-8,-1,0,1,2,5,2,9,0,9,8,5,8,1,0,-1,-2,-5,-2,-9,0,-9,-8,-5,-8,-1,0,1,2,5,2,9,0,9,8 %N A131201 Period 24: repeat [0,1,2,5,2,9,0,9,8,5,8,1,0,-1,-2,-5,-2,-9,0,-9,-8,-5,-8,-1]. %H A131201 <a href="/index/Rec#order_12">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,0,0,0,0,0,0,-1). %F A131201 O.g.f.: x(x^2+1)(x^8+8x^7+4x^6+5x^4+4x^2+2x+1)/((x^4+1)(x^8-x^4+1)) . Also a(n)=b(n-2)+b(n), n>=2, where b(n) = 1, 2, 4, 0, 5, 0, 4, 8, 1, 0, 0, 0, -1, -2, -4, 0, -5, 0, -4, -8, -1, 0, 0, 0, extended with period 24. - _R. J. Mathar_, Jan 15 2008 %o A131201 (PARI) a(n)=[0,1,2,5,2,9,0,9,8,5,8,1][n%12+1]*(-1)^(n\12) \\ _Charles R Greathouse IV_, Jul 26 2016 %K A131201 sign,easy %O A131201 0,3 %A A131201 _Paul Curtz_, Sep 26 2007