Triangle T(n,k) of elements of n-th Weyl group of type B whose reduced word uses n-k generators.

Terms

a(0) =1a(1) =1a(2) =1a(3) =5a(4) =2a(5) =1a(6) =35a(7) =9a(8) =3a(9) =1a(10) =309a(11) =56a(12) =14a(13) =4a(14) =1a(15) =3287a(16) =443a(17) =84a(18) =20a(19) =5a(20) =1a(21) =41005a(22) =4298a(23) =623a(24) =120a(25) =27a(26) =6a(27) =1a(28) =588487a(29) =49937