Table read by antidiagonals: T(n,k) is the number of idempotent n X n 0..k matrices of rank 1.

Terms

a(0) =1a(1) =1a(2) =6a(3) =1a(4) =10a(5) =27a(6) =1a(7) =14a(8) =69a(9) =108a(10) =1a(11) =18a(12) =123a(13) =404a(14) =405a(15) =1a(16) =22a(17) =195a(18) =892a(19) =2155a(20) =1458a(21) =1a(22) =26a(23) =273a(24) =1716a(25) =5845a(26) =10830a(27) =5103a(28) =1a(29) =30