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 A113968 #19 Aug 30 2022 06:40:56 %S A113968 0,0,1,1,15,17,239,273,3823,4369,61167,69905,978671,1118481,15658735, %T A113968 17895697,250539759,286331153,4008636143,4581298449,64138178287, %U A113968 73300775185,1026210852591,1172812402961,16419373641455,18764998447377 %N A113968 a(0) = 0 and a(n) = (5*(-4)^n + 16*(-1)^n + 9*4^n)/240 for n >= 1. %H A113968 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (-1,16,16). %F A113968 From _Colin Barker_, Dec 03 2012: (Start) %F A113968 a(n) = (5*(-4)^n + 16*(-1)^n + 9*4^n)/240 for n>0. %F A113968 G.f.: -x^2*(2*x+1) / ((x+1)*(4*x-1)*(4*x+1)). (End) %t A113968 a[n_] := If[n == 0, 1, (5(-4)^n + 16(-1)^n + 9*4^n) / 240]; %t A113968 a /@ Range[0, 25] (* _Jean-François Alcover_, Mar 30 2021 *) %Y A113968 Cf. A112627. %K A113968 nonn,easy %O A113968 0,5 %A A113968 _Roger L. Bagula_, Jan 31 2006 %E A113968 New name (using _Colin Barker_'s formula) from _Joerg Arndt_, Aug 30 2022