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 A107703 #5 Dec 02 2016 22:11:24
%S A107703 1,2,4,11,43,218,1336,9557,78053,714578,7223548,79704015,951626175,
%T A107703 12210506762,167413540912,2440529176297,37665520151241,
%U A107703 613124748803618,10492684074110772,188241358671950227,3531254422923432083
%N A107703 Sums of antidiagonals of number array A103209.
%C A107703 Row sums of A107702.
%F A107703 a(n)=sum{k=0..n, sum{j=0..n-k, C(n-k+j, 2j)*k^j*C(k)}}, C(n) given by A000108.
%K A107703 easy,nonn
%O A107703 0,2
%A A107703 _Paul Barry_, May 21 2005