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 A084356 #2 Mar 31 2012 13:21:56 %S A084356 1,0,0,0,0,1,5,16,50,137,377,995,2617,6785,17630,45646,118595,308645, %T A084356 806617,2115455,5572438,14737430,39139779,104354064,279293860, %U A084356 750182992,2021884234,5466813137,14826008106,40322237818,109957234707 %N A084356 A000055(n+2)-A023359(n). %Y A084356 Cf. A000055, A023359. %K A084356 nonn %O A084356 0,7 %A A084356 _Jon Perry_, Jun 22 2003