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 A110324 #4 Mar 30 2012 18:59:09 %S A110324 1,-1,1,-4,-2,1,0,-12,-3,1,0,0,-24,-4,1,0,0,0,-40,-5,1,0,0,0,0,-60,-6, %T A110324 1,0,0,0,0,0,-84,-7,1,0,0,0,0,0,0,-112,-8,1,0,0,0,0,0,0,0,-144,-9,1,0, %U A110324 0,0,0,0,0,0,0,-180,-10,1,0,0,0,0,0,0,0,0,0,-220,-11,1,0,0,0,0,0,0,0,0,0,0,-264,-12,1 %N A110324 Inverse of a number triangle related to the Jacobsthal numbers. %C A110324 Row sums are A110325. Diagonal sums are A110326. Inverse of A110321. The result can be generalized as follows: The triangle whose columns have e.g.f. (x^k/k!)/(1-a*x-b*x^2) has inverse T(n,k)=if(n=k,1,if(n-k=1,-a*binomial(n,1),if(n-k=2,-2*b*binomial(n,2),0))) %F A110324 T(n, k)=if(n=k, 1, if(n-k=1, -binomial(n, 1), if(n-k=2, -4*binomial(n, 2), 0))) %e A110324 Rows begin %e A110324 1; %e A110324 -1,1; %e A110324 -4,-2,1; %e A110324 0,-12,-3,1; %e A110324 0,0,-24,-4,1; %e A110324 0,0,0,-40,-5,1; %e A110324 0,0,0,0,-60,-6,1; %K A110324 easy,sign,tabl %O A110324 0,4 %A A110324 _Paul Barry_, Jul 20 2005