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 A128597 #3 Mar 30 2012 18:37:03
%S A128597 1,7,46,297,1919,12399,80241,520399,3382588,22034519,143826980,
%T A128597 940569228,6161492611,40426009162,265617089899,1747501590554,
%U A128597 11510584144337,75901841055650,501007227527884,3310076954166501
%N A128597 Column 2 of triangle A128596; a(n) = coefficient of q^(2n+4) in the q-analog of the even double factorials (2n+4)!! for n>=0.
%F A128597 a(n) = [q^(2n+4)] Product_{j=1..n+2} (1-q^(2j))/(1-q) for n>=0.
%o A128597 (PARI) {a(n)=polcoeff(prod(j=1,n+2,(1-q^(2*j))/(1-q)),2*n+4,q)}
%Y A128597 Cf. A128596; A128084; A000165 ((2n)!!); A128086 (column 1), A128598 (column 3).
%K A128597 nonn
%O A128597 0,2
%A A128597 _Paul D. Hanna_, Mar 12 2007