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 A047141 #5 Mar 30 2012 18:56:53
%S A047141 1,2,4,6,12,20,40,80,160,320,578,1156,2132,4264,8528,17056,34112,
%T A047141 64384,128768,245292,490584,981168,1962336,3924672,7556046,15112092,
%U A047141 29246744,58493488,116986976,233973952,467947904,911000006,1822000012
%N A047141 Sum{T(i,n-i): i=0,1,...,n}, array T as in A047140.
%K A047141 nonn
%O A047141 0,2
%A A047141 _Clark Kimberling_