Triangle read by rows: T(n,k) is the number of commutative groupoids with n elements and k idempotents.

A038021

Triangle read by rows: T(n,k) is the number of commutative groupoids with n elements and k idempotents.

Terms

    a(0) =1a(1) =0a(2) =1a(3) =1a(4) =2a(5) =1a(6) =38a(7) =57a(8) =27a(9) =7a(10) =13872a(11) =18544a(12) =9280a(13) =2080a(14) =192a(15) =83360520a(16) =104208775a(17) =52110500a(18) =13035000a(19) =1632750a(20) =82355a(25) =244914392652a(26) =19596407976a(27) =653502972

External references