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 A123934 #5 Sep 08 2013 13:30:58
%S A123934 1,2,2,3,7,3,4,16,16,4,5,30,51,30,5,6,50,126,126,50,6,7,77,266,393,
%T A123934 266,77,7
%N A123934 Triangle T(n,k), 1<=k<=n :forms the odd-indexed trinomial coefficients (A027907).
%F A123934 Sum_{k, 1<=k<=n}T(n,k)=A003462(n)=(3^n-1)/2.
%e A123934 Triangle begins:
%e A123934 1;
%e A123934 2, 2;
%e A123934 3, 7, 3;
%e A123934 4, 16, 16, 4;
%e A123934 5, 30, 51, 30, 5;
%e A123934 6, 50, 126, 126, 50, 6;
%e A123934 7, 77, 266, 393, 266, 77, 7;
%Y A123934 Cf. A056241.
%K A123934 nonn,tabl
%O A123934 1,2
%A A123934 _Philippe Deléham_, Oct 30 2006