Triangle read by rows: number of 321-avoiding ordered set partitions of [n] into k blocks, n>=1, 1<=k<=n.
A227159
Triangle read by rows: number of 321-avoiding ordered set partitions of [n] into k blocks, n>=1, 1<=k<=n.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =1a(4) =6a(5) =5a(6) =1a(7) =14a(8) =27a(9) =14a(10) =1a(11) =30a(12) =99a(13) =112a(14) =42a(15) =1a(16) =62a(17) =307a(18) =564a(19) =450a(20) =132a(21) =1a(22) =126a(23) =867a(24) =2284a(25) =2895a(26) =1782a(27) =429a(28) =1a(29) =254
External references
- oeis: A227159