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 A203196 #7 Oct 15 2013 14:41:04
%S A203196 1,3,14,50,324,1764,14832,109584,1136160,10628640,131172480,
%T A203196 1486442880,21289201920,283465647360,4622628648960,70734282393600,
%U A203196 1294139872972800,22376988058521600,453942134876160000,8752948036761600000
%N A203196 (n-1)-st elementary symmetric function of the first n terms of (2,1,4,3,6,5,8,7,...)=A103889.
%C A203196 a(2n)=A000254(2n) for n=1,2,3...
%t A203196 f[k_] := If[Mod[k, 2] == 0, k - 1, k + 1]
%t A203196 t[n_] := Table[f[k], {k, 1, n}]
%t A203196 a[n_] := SymmetricPolynomial[n - 1, t[n]]
%t A203196 Table[a[n], {n, 1, 14}] (* A203196 *)
%Y A203196 Cf. A103889.
%K A203196 nonn
%O A203196 1,2
%A A203196 _Clark Kimberling_, Dec 30 2011