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 A087946 #11 Jun 13 2015 00:51:15 %S A087946 1,3,10,35,126,461,1702,6315,23494,87533,326382,1217483,4542526, %T A087946 16950573,63255670,236063915,880983606,3287837741,12270301822, %U A087946 45793238475,170902389934,637815796973,2380359749382,8883621103403 %N A087946 Expansion of (1-3x+x^2)/((1-2x)(1-4x+x^2)). %C A087946 Binomial transform of A057960. %H A087946 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (6,-9,2). %F A087946 a(0)=1, a(1)=3, a(2)=10, a(n)=6a(n-1)-9a(n-2)+2a(n-3), n>2. %F A087946 a(n) = 2^n/3+(2+sqrt(3))(2+sqrt(3))^n/6+(2-sqrt(3))(2-sqrt(3))^n/6. %F A087946 a(n) = A087944(n+1)/2. %K A087946 easy,nonn %O A087946 0,2 %A A087946 _Paul Barry_, Sep 16 2003