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 A127800 #6 Sep 30 2018 02:35:36 %S A127800 1,0,2,0,-2,2,0,2,-2,2,0,0,0,-2,2,0,-2,2,0,-2,2,0,0,0,0,0,-2,2,0,2,-2, %T A127800 2,0,0,-2,2,0,0,0,0,0,0,0,-2,2,0,0,0,-2,2,0,0,0,-2,2,0,0,0,0,0,0,0,0, %U A127800 0,-2,2,0,-2,2,0,-2,2,0,0,0,0,-2,2 %N A127800 Inverse of number triangle A(n,k) = 1/(2 - 0^n), if k <= n <= 2k, 0 otherwise. %C A127800 Row sums are A069517 (conjecture). %e A127800 Triangle begins %e A127800 1; %e A127800 0, 2; %e A127800 0, -2, 2; %e A127800 0, 2, -2, 2; %e A127800 0, 0, 0, -2, 2; %e A127800 0, -2, 2, 0, -2, 2; %e A127800 0, 0, 0, 0, 0, -2, 2; %e A127800 0, 2, -2, 2, 0, 0, -2, 2; %e A127800 0, 0, 0, 0, 0, 0, 0, -2, 2; %e A127800 0, 0, 0, -2, 2, 0, 0, 0, -2, 2; %e A127800 0, 0, 0, 0, 0, 0, 0, 0, 0, -2, 2; %e A127800 0, -2, 2, 0, -2, 2, 0, 0, 0, 0, -2, 2; %e A127800 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -2, 2; %e A127800 Inverse of triangle begins %e A127800 1; %e A127800 0, 1/2; %e A127800 0, 1/2, 1/2; %e A127800 0, 0, 1/2, 1/2; %e A127800 0, 0, 1/2, 1/2, 1/2; %e A127800 0, 0, 0, 1/2, 1/2, 1/2; %e A127800 0, 0, 0, 1/2, 1/2, 1/2, 1/2; %e A127800 0, 0, 0, 0, 1/2, 1/2, 1/2, 1/2; %e A127800 0, 0, 0, 0, 1/2, 1/2, 1/2, 1/2, 1/2; %e A127800 0, 0, 0, 0, 0, 1/2, 1/2, 1/2, 1/2, 1/2; %e A127800 0, 0, 0, 0, 0, 1/2, 1/2, 1/2, 1/2, 1/2, 1/2; %K A127800 sign,tabl %O A127800 0,3 %A A127800 _Paul Barry_, Jan 29 2007