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 A047111 #5 Mar 30 2012 18:56:53
%S A047111 1,2,3,6,10,20,40,71,142,260,520,1040,1936,3872,7330,14660,29320,
%T A047111 55874,111748,215252,430504,861008,1663662,3327324,6476960,12953920,
%U A047111 25907840,50511295,101022590,198016168,396032336,792064672,1553798279
%N A047111 Sum{T(i,n-i): i=0,1,...,n}, array T as in A047110.
%K A047111 nonn
%O A047111 0,2
%A A047111 _Clark Kimberling_