a(n) = floor(n!/sigma(n)).

Terms

a(0) =1a(1) =0a(2) =1a(3) =3a(4) =20a(5) =60a(6) =630a(7) =2688a(8) =27913a(9) =201600a(10) =3326400a(11) =17107200a(12) =444787200a(13) =3632428800a(14) =54486432000a(15) =674928706064