2nd diagonal (from right) in A104978.

Terms

a(0) =2a(1) =21a(2) =180a(3) =1430a(4) =10920a(5) =81396a(6) =596904a(7) =4326300a(8) =31081050a(9) =221760825a(10) =1573537680a(11) =11114897976a(12) =78215948720a(13) =548652722520