a(n) = n! * number of partitions of n.

Terms

a(0) =1a(1) =1a(2) =4a(3) =18a(4) =120a(5) =840a(6) =7920a(7) =75600a(8) =887040a(9) =10886400a(10) =152409600a(11) =2235340800a(12) =36883123200a(13) =628929100800