a(1) = 1; a(n) = n * Sum_{k=1..n-1} a(k).

Terms

a(0) =1a(1) =2a(2) =9a(3) =48a(4) =300a(5) =2160a(6) =17640a(7) =161280a(8) =1632960a(9) =18144000a(10) =219542400a(11) =2874009600a(12) =40475635200a(13) =610248038400