Number T(n,k) of k up, k down permutations of [n]; triangle T(n,k), n>=0, 0<=k<=n, read by rows.

Terms

a(0) =1a(1) =1a(2) =1a(3) =0a(4) =1a(5) =1a(6) =0a(7) =2a(8) =1a(9) =1a(10) =0a(11) =5a(12) =3a(13) =1a(14) =1a(15) =0a(16) =16a(17) =6a(18) =4a(19) =1a(20) =1a(21) =0a(22) =61a(23) =26a(24) =10a(25) =5a(26) =1a(27) =1a(28) =0a(29) =272