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 A108075 #16 Jan 25 2020 02:34:00 %S A108075 1,1,1,3,3,1,9,9,5,1,31,31,19,7,1,113,113,73,33,9,1,431,431,287,143, %T A108075 51,11,1,1697,1697,1153,609,249,73,13,1,6847,6847,4719,2591,1151,399, %U A108075 99,15,1,28161,28161,19617,11073,5201,2001,601,129,17,1,117631,117631,82623 %N A108075 Triangle in A071945 with rows reversed. %H A108075 D. Baccherini, D. Merlini and R. Sprugnoli, <a href="http://pefmath.etf.rs/vol2num1/AADM-Vol2-No1-69-91.pdf">Level generating trees and proper Riordan arrays</a>, Applicable Analysis and Discrete Mathematics, 2, 2008, 69-91 (see p. 88). [From _Emeric Deutsch_, Sep 21 2008] %F A108075 G.f.: (1-q)/(z(1+z)(2-t+tq)), where q = sqrt(1 - 4z - 4z^2). - _Emeric Deutsch_, Jun 06 2005 %F A108075 T(n,k) = T(n-1,k-1) + T(n-2,k-1) + T(n,k+1), T(0,0)=1. - _Philippe Deléham_, Nov 18 2009 %e A108075 Triangle begins: %e A108075 1; %e A108075 1, 1; %e A108075 3, 3, 1; %e A108075 9, 9, 5, 1; %e A108075 31, 31, 19, 7, 1; %e A108075 ... %p A108075 q:=sqrt(1-4*z-4*z^2): G:=(1-q)/z/(1+z)/(2-t+t*q): Gser:=simplify(series(G,z=0,13)): P[0]:=1: for n from 1 to 10 do P[n]:=coeff(Gser,z^n) od: for n from 0 to 10 do seq(coeff(t*P[n],t^k),k=1..n+1) od; # yields sequence in triangular form - _Emeric Deutsch_, Jun 06 2005 %Y A108075 Row sums yield A052705. Column 0 yields A052709. %K A108075 nonn,tabl,easy %O A108075 0,4 %A A108075 _N. J. A. Sloane_, Jun 05 2005 %E A108075 More terms from _Emeric Deutsch_, Jun 06 2005