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 A181652 #2 Mar 30 2012 18:59:28 %S A181652 1,-1,1,-1,-1,1,-1,0,-1,1,-1,0,-1,-1,1,-1,0,-1,0,-1,1,-1,0,-1,0,-1,-1, %T A181652 1,-1,0,-1,0,-1,0,-1,1,-1,0,-1,0,-1,0,-1,-1,1,-1,0,-1,0,-1,0,-1,0,-1, %U A181652 1,-1,0,-1,0,-1,0,-1,0,-1,-1,1 %N A181652 Inverse of number triangle A181651. %C A181652 Generalized (conditional) Riordan array with k-th column generated by x^k*if(mod(k,2)=0,(1-2x)/(1-x),1-x). %e A181652 Triangle begins %e A181652 1, %e A181652 -1, 1, %e A181652 -1, -1, 1, %e A181652 -1, 0, -1, 1, %e A181652 -1, 0, -1, -1, 1, %e A181652 -1, 0, -1, 0, -1, 1, %e A181652 -1, 0, -1, 0, -1, -1, 1, %e A181652 -1, 0, -1, 0, -1, 0, -1, 1, %e A181652 -1, 0, -1, 0, -1, 0, -1, -1, 1, %e A181652 -1, 0, -1, 0, -1, 0, -1, 0, -1, 1, %e A181652 -1, 0, -1, 0, -1, 0, -1, 0, -1, -1, 1 %e A181652 Production matrix begins %e A181652 -1, 1, %e A181652 0, -2, 1, %e A181652 1, 0, -2, 1, %e A181652 1, -1, 0, -2, 1, %e A181652 2, -1, 1, 0, -2, 1, %e A181652 2, -1, 1, -1, 0, -2, 1, %e A181652 3, -1, 2, -1, 1, 0, -2, 1, %e A181652 3, -1, 2, -1, 1, -1, 0, -2, 1, %e A181652 4, -1, 3, -1, 2, -1, 1, 0, -2, 1 %Y A181652 Cf. A070909. %K A181652 easy,sign,tabl %O A181652 0,1 %A A181652 _Paul Barry_, Nov 03 2010