Number of reduced words of length n in the Weyl group B_20.

Terms

a(0) =1a(1) =20a(2) =209a(3) =1520a(4) =8644a(5) =40944a(6) =168035a(7) =613756a(8) =2034120a(9) =6206596a(10) =17632836a(11) =47062620a(12) =118870650a(13) =285840940a(14) =657667521a(15) =1454009144a(16) =3100176535a(17) =6394814820a(18) =12796122680a(19) =24898749084a(20) =47210910670a(21) =87394933100a(22) =158210114490a(23) =280501919100a(24) =487725336449a(25) =832684355656