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 A108931 #6 Sep 11 2019 04:37:15 %S A108931 0,1,-3,8,-18,47,-105,274,-612,1597,-3567,9308,-20790,54251,-121173, %T A108931 316198,-706248,1842937,-4116315,10741424,-23991642,62605607, %U A108931 -139833537,364892218,-815009580,2126747701,-4750223943,12395593988,-27686334078,72246816227 %N A108931 a(2n) = -A106328(n), a(2n+1) = A054488(n). %H A108931 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,6,0,-1). %F A108931 G.f. x*(2*x-1)*(x-1)/((x^2+2*x-1)*(x^2-2*x-1)) %p A108931 seriestolist(series(x*(2*x-1)*(x-1)/((x^2+2*x-1)*(x^2-2*x-1)), x=0,30)); -or- Floretion Algebra Multiplication Program, FAMP Code: 1jescycrokseq[ + 'jj' + 'kk' + 'ij'] Roktype is set to: Y[sqa.Findk()] = Y[sqa.Findk()] + 1/2; %Y A108931 Cf. A106328, A054488. %K A108931 easy,sign %O A108931 0,3 %A A108931 _Creighton Dement_, Jul 20 2005