a(n) = Hermite(n,6).

Terms

a(0) =1a(1) =12a(2) =142a(3) =1656a(4) =19020a(5) =214992a(6) =2389704a(7) =26096544a(8) =279702672a(9) =2938887360a(10) =30232000224a(11) =304006255488