Number of binary operations on an n-set that are commutative and associative; labeled commutative semigroups.
A023815
Number of binary operations on an n-set that are commutative and associative; labeled commutative semigroups.
Terms
- a(0) =1a(1) =1a(2) =6a(3) =63a(4) =1140a(5) =30730a(6) =1185072a(7) =66363206a(8) =7150843144
External references
- oeis: A023815