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 A110323 #6 Oct 08 2016 12:07:03
%S A110323 1,1,7,32,283,2643,32317,443824,7115461,127222805,2541399091,
%T A110323 55739417376,1335729425647,34666455314407,969419191792633,
%U A110323 29046504524166368,928541094344685577,31540972026299055849
%N A110323 Diagonal sums of a number triangle related to the Jacobsthal numbers.
%C A110323 Diagonal sums of number triangle A110321.
%F A110323 a(n)=sum{k=0..floor(n/2), (n-k)!*J(n-2k+1)/k!}, J(n)=A001045(n).
%t A110323 J[n_] := (2^n-(-1)^n)/3; a[n_] := Sum[(n-k)!*J[n-2*k+1]/k!, {k, 0, n/2}]; Table[a[n], {n, 0, 17}] (* _Jean-François Alcover_, Oct 08 2016 *)
%K A110323 easy,nonn
%O A110323 0,3
%A A110323 _Paul Barry_, Jul 20 2005