a(0)=0, a(n) = (a(n-1) * n) OR n.

Terms

a(0) =0a(1) =1a(2) =2a(3) =7a(4) =28a(5) =141a(6) =846a(7) =5927a(8) =47416a(9) =426745a(10) =4267450a(11) =46941951a(12) =563303420a(13) =7322944461a(14) =102521222462