Triangle read by rows: number of idempotents of rank k in partition monoid P_n.

Terms

a(0) =1a(1) =1a(2) =1a(3) =4a(4) =7a(5) =1a(6) =25a(7) =70a(8) =18a(9) =1a(10) =225a(11) =921a(12) =331a(13) =34a(14) =1a(15) =2704a(16) =15191a(17) =6880a(18) =995a(19) =55a(20) =1a(21) =41209a(22) =304442a(23) =163336a(24) =29840a(25) =2345a(26) =81a(27) =1a(28) =769129a(29) =7240353