Number of commutative semigroups of order n.

A001426

Number of commutative semigroups of order n.

Terms

    a(0) =1a(1) =1a(2) =3a(3) =12a(4) =58a(5) =325a(6) =2143a(7) =17291a(8) =221805a(9) =11545843a(10) =3518930337

External references