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 A111963 #4 Mar 30 2012 18:59:12
%S A111963 1,-1,1,-1,-2,1,3,-1,-3,1,1,8,0,-4,1,-9,-3,14,2,-5,1,1,-26,-15,20,5,
%T A111963 -6,1,27,27,-45,-37,25,9,-7,1,-13,76,98,-56,-70,28,14,-8,1,-81,-135,
%U A111963 108,228,-46,-114,28,20,-9,1,67,-202,-459,48,420,0,-168,24,27,-10,1,243,567,-135,-1035,-210,662,98,-230,15,35,-11,1,-285
%N A111963 Inverse of renewal array for central trinomial numbers.
%C A111963 Row sums have g.f. 1/sqrt(1+4x^2) [alternating sign central binomial numbers with interpolated zeros]. Diagonal sums are A111964. Inverse of A111960. Factors as (1/sqrt(1+4x^2),x/sqrt(1+4x^2))*(1/(1+x),x/(1+x)).
%F A111963 Riordan array (1/(sqrt(1+4x^2)+x), x/(sqrt(1+4x^2)+x)); Number triangle T(n, k)=sum{i=0..floor(n/2), C(2i+k-n-1, k)*C((2i-n-1)/2, i)(-1)^n*4^i}.
%e A111963 Triangle begins
%e A111963 1;
%e A111963 -1,1;
%e A111963 -1,-2,1;
%e A111963 3,-1,-3,1;
%e A111963 1,8,0,-4,1;
%e A111963 -9,-3,14,2,-5,1;
%e A111963 1,-26,-15,20,5,-6,1;
%K A111963 easy,sign,tabl
%O A111963 0,5
%A A111963 _Paul Barry_, Aug 23 2005