Product{k|n} k$. Here '$' denotes the swinging factorial function (A056040).

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =12a(5) =30a(6) =240a(7) =140a(8) =840a(9) =3780a(10) =15120a(11) =2772a(12) =1330560a(13) =12012a(14) =960960a(15) =9266400a(16) =10810800a(17) =218790a(18) =7351344000a(19) =923780a(20) =16761064320a(21) =3259095840a(22) =3910915008a(23) =16224936a(25) =2028117000a(26) =249864014400