n! divided by its squarefree kernel.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =4a(5) =4a(6) =24a(7) =24a(8) =192a(9) =1728a(10) =17280a(11) =17280a(12) =207360a(13) =207360a(14) =2903040a(15) =43545600a(16) =696729600a(17) =696729600a(18) =12541132800a(19) =12541132800a(20) =250822656000