Triangle read by rows: T(0,0)=1; T(m,0)=0; otherwise T(m,n) = (m-1)*T(m-1,n)+(m-1+n)*T(m-1,n-1).

Terms

a(0) =1a(1) =0a(2) =1a(3) =0a(4) =1a(5) =3a(6) =0a(7) =2a(8) =10a(9) =15a(10) =0a(11) =6a(12) =40a(13) =105a(14) =105a(15) =0a(16) =24a(17) =196a(18) =700a(19) =1260a(20) =945a(21) =0a(22) =120a(23) =1148a(24) =5068a(25) =12600a(26) =17325a(27) =10395a(28) =0a(29) =720