Number of labeled groups.

Terms

a(0) =1a(1) =2a(2) =3a(3) =16a(4) =30a(5) =480a(6) =840a(7) =22080a(8) =68040a(9) =1088640a(10) =3991680a(11) =259459200a(12) =518918400a(13) =16605388800a(14) =163459296000