Triangle read by rows: S_B(n,k) = "Type B" Stirling numbers of the second kind.

Terms

a(0) =2a(1) =2a(2) =5a(3) =2a(4) =15a(5) =14a(6) =2a(7) =35a(8) =84a(9) =43a(10) =2a(11) =75a(12) =350a(13) =430a(14) =142a(15) =2a(16) =155a(17) =1260a(18) =2795a(19) =2130a(20) =499a(21) =2a(22) =315a(23) =4214a(24) =15050a(25) =19880a(26) =10479a(27) =1850a(28) =2a(29) =635