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 A112476 #10 Sep 07 2024 08:55:02
%S A112476 1,-1,2,0,3,3,8,12,25,43,82,148,275,503,928,1704,3137,5767,10610,
%T A112476 19512,35891,66011,121416,223316,410745,755475,1389538,2555756,
%U A112476 4700771,8646063,15902592,29249424,53798081,98950095,181997602,334745776,615693475,1132436851,2082876104,3831006428
%N A112476 Diagonal sums of Riordan array (1/(1+x),x(1+x)/(1-x)).
%C A112476 Diagonal sums of A112475.
%H A112476 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,2,2,1).
%F A112476 G.f.: (1-x)/((1+x)*(1-x-x^2-x^3)).
%F A112476 a(n) = 2*a(n-2)+2*a(n-3)+a(n-4).
%F A112476 a(n) = Sum_{k=0..floor(n/2)} Sum_{j=0..n-2*k} C(k-1, j)*C(n-k-j-1, n-2*k-j).
%K A112476 easy,sign
%O A112476 0,3
%A A112476 _Paul Barry_, Sep 07 2005