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 A126127 #10 Jul 07 2019 20:20:09 %S A126127 1,-2,1,-1,-2,1,5,-3,-2,1,2,9,-5,-2,1,-13,9,13,-7,-2,1,-5,-33,20,17, %T A126127 -9,-2,1,34,-27,-61,35,21,-11,-2,1,13,111,-73,-97,54,25,-13,-2,1,-89, %U A126127 80,248,-151,-141,77,29,-15,-2,1,-34,-355,252,461,-269,-193,104,33,-17,-2,1 %N A126127 Inverse square of A061554. %C A126127 Inverse of A061554 = A046854; therefore A126127 = (A046854)^2. %H A126127 Robert Israel, <a href="/A126127/b126127.txt">Table of n, a(n) for n = 0..10009</a> (rows 0 to 140, flattened) %F A126127 Given M = Pascal's triangle with descending row terms, (A061554); A126127 = M^(-2). %F A126127 G.f. as triangle (conjectured): (1-x)*(1-x+x^2)/(1-x*y+3*x^2-x^3*y+x^4). - _Robert Israel_, Jul 07 2019 %e A126127 First few rows of the triangle are: %e A126127 1; %e A126127 -2, 1; %e A126127 -1, -2, 1; %e A126127 5, -3, -2, 1; %e A126127 2, 9, -5, -2, 1; %e A126127 -13, 9, 13, -7, -2, 1; %e A126127 ... %p A126127 T:= Matrix(20,20,(n,k) -> binomial(n-1, floor((n)/2 - (-1)^(n-k)*(k)/2)), shape=triangular[lower]): %p A126127 A:= T^(-2): %p A126127 seq(seq(A[i,k],k=1..i),i=1..20); # _Robert Israel_, Jul 07 2019 %Y A126127 Cf. A061554, A046854. %K A126127 tabl,sign %O A126127 0,2 %A A126127 _Gary W. Adamson_, Dec 17 2006