Number of labeled groups with a fixed identity.

Terms

a(0) =1a(1) =1a(2) =1a(3) =4a(4) =6a(5) =80a(6) =120a(7) =2760a(8) =7560a(9) =108864a(10) =362880a(11) =21621600a(12) =39916800a(13) =1186099200a(14) =10897286400a(15) =647091244800