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 A112294 #3 Mar 30 2012 18:59:12
%S A112294 1,1,4,18,121,1055,11376,145852,2165689,36532197,689873284,
%T A112294 14415662558,330204013569,8226714806323,221470234531456,
%U A112294 6406397898751320,198160750081637521,6526636388676159977,228040136335670652324
%N A112294 Diagonal sums of number triangle A112292.
%F A112294 a(n)=sum{k=0..floor(n/2), (2n-2k-1)!!/(2k-1)!!}; a(n)=sum{k=0..floor(n/2), 2^(n-2k)(n-k-1/2)!/(k-1/2)!}; a(n)=sum{k=0..floor(n/2), (n-k)!C(2n-2k, n-k)2^(2k-n)/(k!C(2k, k))}; a(n)=sum{k=0..floor(n/2), (n-k+1)!*C(n-k)2^(2k-n)/((k+1)!*C(k))}.
%K A112294 easy,nonn
%O A112294 0,3
%A A112294 _Paul Barry_, Sep 01 2005