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 A165204 #15 Feb 15 2018 20:46:11 %S A165204 1,-5,-21,-21,89,377,377,-1597,-6765,-6765,28657,121393,121393, %T A165204 -514229,-2178309,-2178309,9227465,39088169,39088169,-165580141, %U A165204 -701408733,-701408733,2971215073,12586269025,12586269025,-53316291173,-225851433717,-225851433717 %N A165204 Hankel transform of A165203. %C A165204 Entries are based on F(3n+2). %F A165204 Conjectures from _Colin Barker_, Feb 10 2018: (Start) %F A165204 G.f.: (1 - 8*x + 2*x^2 - x^3) / (1 - 3*x + 8*x^2 - 3*x^3 + x^4). %F A165204 a(n) = 3*a(n-1) - 8*a(n-2) + 3*a(n-3) - a(n-4) for n>3. %F A165204 (End) %K A165204 sign %O A165204 0,2 %A A165204 _Paul Barry_, Sep 07 2009 %E A165204 More terms added, and a(19) corrected by _Colin Barker_, Feb 10 2018