Isomorphism classes of 2-in 2-out regular digraphs, allowing parallel edges but not loops.
A307180
Isomorphism classes of 2-in 2-out regular digraphs, allowing parallel edges but not loops.
Terms
- a(0) =1a(1) =0a(2) =1a(3) =2a(4) =6a(5) =15a(6) =68a(7) =310a(8) =2096a(9) =16554a(10) =152497a(11) =1574652a(12) =17947667a(13) =223013311
External references
- oeis: A307180