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 A172026 #3 Sep 08 2013 13:31:52
%S A172026 1,0,1,1,0,1,0,2,0,1,3,0,3,0,1,0,7,0,4,0,1,12,0,12,0,5,0,1,0,30,0,18,
%T A172026 0,6,0,1,55,0,55,0,25,0,7,0,1,0,143,0,88,0,33,0,8,0,1,273,0,273,0,130,
%U A172026 0,42,0,9,0,1,0,728,0,455,0,182,0,52,0,10,0,1,1428,0,1428,0,700,0,245,0
%N A172026 Riordan array (f(x^2), x*f(x^2)) where f(x) is the g.f. of A001764.
%C A172026 Another version of A110616. Riordan production matrix is: (x/(1-x^2), 1/(1-x^2)).
%F A172026 Sum_{k, 0<=k<=n} T(n,k)= A047749(n+1).
%e A172026 Triangle begins : 1 ; 0,1 ; 1,0,1 ; 0,2,0,1 ; 3,0,3,0,1 ; 0,7,0,4,0,1 ; 12,0,12,0,5,0,1 ; ...
%Y A172026 Cf. A047749, A092276, A143603
%K A172026 nonn,tabl
%O A172026 0,8
%A A172026 _Philippe Deléham_, Jan 23 2010