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 A055300 #6 Mar 30 2012 17:37:10 %S A055300 1,-1,1,0,-1,1,1,0,-2,1,0,1,0,-2,1,-3,1,4,0,-3,1,-1,-3,2,4,0,-3,1,14, %T A055300 -10,-15,4,10,0,-4,1,20,11,-36,-12,11,9,0,-4,1,-77,92,76,-67,-56,16, %U A055300 20,0,-5,1,-308,92,421,-24,-200,-24,30,17,0,-5,1,147,-994,200,847,196 %N A055300 Matrix inverse of triangle A055290(n+1,k). %H A055300 <a href="/index/Tra#trees">Index entries for sequences related to trees</a> %e A055300 1; -1,1; 0,-1,1; 1,0,-2,1; 0,1,0,-2,1; ... %K A055300 sign,tabl %O A055300 2,9 %A A055300 _Christian G. Bower_, May 09 2000