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 A202551 #6 Feb 22 2013 14:40:24
%S A202551 1,1,-1,0,-1,1,-1,1,1,-1,-1,3,-2,-1,1,0,2,-5,3,1,-1,1,-2,-2,7,-4,-1,1,
%T A202551 1,-5,7,1,-9,5,1,-1,0,-3,12,-15,1,11,-6,-1,1,-1,3,3,-21,26,-4,-13,7,1,
%U A202551 -1
%N A202551 Triangle T(n,k), read by rows, given by (1, -1, 1, 0, 0, 0, 0, 0, 0, 0, ...) DELTA (-1, 0, 0, 0, 0, 0, 0, 0, 0, 0, ...) where DELTA is the operator defined in A084938.
%C A202551 Riordan array (1/(1-x+x^2), x*(x-1)/(1-x+x^2)).
%F A202551 T(n,k) = T(n-1,k) + T(n-2,k-1) - T(n-1,k-1) - T(n-2,k).
%F A202551 G.f.: 1/(1+(y-1)*x+(1-y)*x^2).
%F A202551 Sum_{k, 0<=k<=n} T(n,k)*x^k = A190873(n+1), A190871(n+1), A057086(n), A057085(n+1), A057084(n), A030240(n), A030192(n), A030191(n), A001787(n+1), A057083(n), A099087(n), A010892(n), A000007(n), (-1)^n*A000045(n+1) for x = -11, -10, -9, -8, -7, -6, -5, -4, -3, -2, -1, 0, 1, 2 respectively.
%e A202551 Triangle begins :
%e A202551 1
%e A202551 1, -1
%e A202551 0, -1, 1
%e A202551 -1, 1, 1, -1
%e A202551 -1, 3, -2, -1, 1
%e A202551 0, 2, -5, 3, 1, -1
%Y A202551 Cf. A129267, A199324
%K A202551 sign,tabl
%O A202551 0,12
%A A202551 _Philippe Deléham_, Dec 21 2011