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

Terms

a(0) =1a(1) =2a(2) =2a(3) =3a(4) =18a(5) =12a(6) =16a(7) =180a(8) =288a(9) =140a(10) =30a(11) =2640a(12) =6540a(13) =8380a(14) =3020a(15) =480a(16) =119610a(17) =238200a(18) =421020a(19) =372360a(20) =100362a(21) =840a(22) =25196052a(23) =13786290a(24) =26803000a(25) =36174600a(26) =22822674a(27) =4768624a(28) =22080a(29) =48687313640