Number of bicoverings of an n-set.

Terms

a(0) =1a(1) =0a(2) =1a(3) =8a(4) =80a(5) =1088a(6) =19232a(7) =424400a(8) =11361786a(9) =361058000a(10) =13386003873a(11) =570886397340