Triangle read by rows: T(n,1)=1, T(n,k) = T(n-1,k) + (n-1)T(n-1, k-1) for 1 <= k <= n.

Terms

a(0) =1a(1) =1a(2) =2a(3) =1a(4) =4a(5) =6a(6) =1a(7) =7a(8) =18a(9) =24a(10) =1a(11) =11a(12) =46a(13) =96a(14) =120a(15) =1a(16) =16a(17) =101a(18) =326a(19) =600a(20) =720a(21) =1a(22) =22a(23) =197a(24) =932a(25) =2556a(26) =4320a(27) =5040a(28) =1a(29) =29