a(1) = 1; for n > 1, a(n) = A055231(a(n-1) * n), where A055231(k) is the powerfree part of k.

Terms

a(0) =1a(1) =2a(2) =6a(3) =3a(4) =15a(5) =10a(6) =70a(7) =35a(8) =35a(9) =14a(10) =154a(11) =231a(12) =3003a(13) =858a(14) =1430a(15) =715a(16) =12155a(17) =24310a(18) =461890a(19) =46189a(20) =969969a(21) =176358a(22) =4056234a(23) =676039a(24) =676039a(25) =104006a(26) =104006a(27) =7429a(28) =215441a(29) =6463230