One half of A075178.

Terms

a(0) =1a(1) =6a(2) =6a(3) =60a(4) =10a(5) =252a(6) =84a(7) =360a(8) =90a(9) =660a(10) =44a(11) =32760a(12) =5460a(13) =2520a(14) =360a(15) =12240a(16) =34a(17) =14364a(18) =1596a(19) =19800a(20) =13860a(21) =91080a(22) =920a(23) =982800a(24) =81900a(25) =19656a(26) =1512a(27) =48720a(28) =1160a(29) =1718640