Matrix square of Stirling2 triangle A008277: 2-levels set partitions of [n] into k first-level subsets.

A039810

Matrix square of Stirling2 triangle A008277: 2-levels set partitions of [n] into k first-level subsets.

Terms

    a(0) =1a(1) =2a(2) =1a(3) =5a(4) =6a(5) =1a(6) =15a(7) =32a(8) =12a(9) =1a(10) =52a(11) =175a(12) =110a(13) =20a(14) =1a(15) =203a(16) =1012a(17) =945a(18) =280a(19) =30a(20) =1a(21) =877a(22) =6230a(23) =8092a(24) =3465a(25) =595a(26) =42a(27) =1a(28) =4140a(29) =40819

External references