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 A140734 #7 Feb 08 2022 20:04:58 %S A140734 1,1,1,1,1,2,4,4,1,1,3,9,18,21,9,1,1,4,16,48,102,132,76,16,1,1,5,25, %T A140734 100,310,690,970,680,205,25,1,1,6,36,180,735,2340,5420,8160,2550,456, %U A140734 36,1,1,7,49,294,1491,6195,20195,48440,778315,70245,32571,7602,889,49,1 %N A140734 Triangle read by rows, X^n * [1,0,0,0,...]; where X = a tridiagonal matrix with (1,1,1,...) in the main and subsubdiagonals and (1,2,3,...) in the subdiagonal. %e A140734 First few rows of the triangle: %e A140734 1; %e A140734 1, 1, 1; %e A140734 1, 2, 4, 4, 1; %e A140734 1, 3, 9, 18, 21, 9, 1; %e A140734 1, 4, 16, 48, 102, 132, 76, 16, 1; %e A140734 1, 5, 25, 100, 310, 690, 970, 680, 205, 25, 1; %e A140734 1, 6, 36, 180, 735, 2340, 5420, 8160, 2550, 456, 36, 1; %e A140734 1, 7, 49, 294, 1491, 6195, 20195, 48440, 77315, 70245, 32571, 7602, 889, 49, 1; %e A140734 ... %Y A140734 Cf. A140733, A140735. %K A140734 nonn,tabl %O A140734 1,6 %A A140734 _Gary W. Adamson_ & _Roger L. Bagula_, May 25 2008