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 A124234 #5 Nov 05 2016 03:39:09
%S A124234 1,1,1,1,3,1,1,4,5,1,1,4,11,7,1,1,4,15,22,9,1,1,4,16,42,37,11,1,1,4,
%T A124234 16,57,93,56,13,1,1,4,16,63,163,176,79,15,1,1,4,16,64,219,386,299,106,
%U A124234 17,1,1,4,16,64,247,638,794,470,137,19,1
%N A124234 Riordan array (1/(1-x), x(1+x)^2).
%C A124234 Row sums are A077864. Diagonal sums are A004695(n+3). T(2n,n) is A032443.
%F A124234 T(n,k) = Sum_{j=0..n-k} C(2k,j).
%e A124234 Triangle begins
%e A124234 1,
%e A124234 1, 1,
%e A124234 1, 3, 1,
%e A124234 1, 4, 5, 1,
%e A124234 1, 4, 11, 7, 1,
%e A124234 1, 4, 15, 22, 9, 1,
%e A124234 1, 4, 16, 42, 37, 11, 1
%o A124234 (PARI) tabl(nn) = for (n=0, nn, for (k=0, n, print1(sum(j=0, n-k, binomial(2*k, j)), ", ")); print();); \\ _Michel Marcus_, Nov 05 2016
%Y A124234 Cf. A004695, A032443, A077864.
%K A124234 easy,nonn,tabl
%O A124234 0,5
%A A124234 _Paul Barry_, Oct 22 2006