a(n) = n! / (a(n-1) a(n-2) a(n-3)), where a(0) = a(1) = a(2) = 1.

Terms

a(0) =1a(1) =1a(2) =1a(3) =6a(4) =4a(5) =5a(6) =6a(7) =42a(8) =32a(9) =45a(10) =60a(11) =462a(12) =384a(13) =585a(14) =840a(15) =6930a(16) =6144a(17) =9945a(18) =15120a(19) =131670a(20) =122880a(21) =208845a(22) =332640a(23) =3028410a(24) =2949120a(25) =5221125a(26) =8648640a(27) =81767070a(28) =82575360a(29) =151412625