Triangle read by rows: T(n,k) is the number of labeled commutative semigroups of order n with k idempotents.

A058167

Triangle read by rows: T(n,k) is the number of labeled commutative semigroups of order n with k idempotents.

Terms

    a(0) =1a(1) =4a(2) =2a(3) =24a(4) =30a(5) =9a(6) =260a(7) =492a(8) =312a(9) =76a(10) =4805a(11) =10060a(12) =9900a(13) =4900a(14) =1065a(15) =157956a(16) =284130a(17) =348420a(18) =259500a(19) =112500a(20) =22566a(21) =12277440a(22) =11892846a(23) =14768775a(24) =14093380a(25) =9063600a(26) =3592554a(27) =674611a(28) =3287166928a(29) =896150920

External references