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 A128598 #3 Mar 30 2012 18:37:03
%S A128598 1,24,297,3210,32510,318171,3054100,28980565,273077443,2562036673,
%T A128598 23973009386,223949654108,2090070431683,19496003736658,
%U A128598 181815760387221,1695523268254637,15813185728272754,147508341317700463
%N A128598 Column 3 of triangle A128596; a(n) = coefficient of q^(3n+9) in the q-analog of the even double factorials (2n+6)!! for n>=0.
%F A128598 a(n) = [q^(3n+9)] Product_{j=1..n+3} (1-q^(2j))/(1-q) for n>=0.
%o A128598 (PARI) {a(n)=polcoeff(prod(j=1,n+3,(1-q^(2*j))/(1-q)),3*n+9,q)}
%Y A128598 Cf. A128596; A128084; A000165 ((2n)!!); A128086 (column 1), A128597 (column 2).
%K A128598 nonn
%O A128598 0,2
%A A128598 _Paul D. Hanna_, Mar 12 2007