Number of standard shifted tableaux with n entries.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =6a(5) =12a(6) =27a(7) =63a(8) =154a(9) =398a(10) =1055a(11) =2970a(12) =8503a(13) =25651a(14) =78483a(15) =250487a(16) =811802a(17) =2723130a(18) =9295483a(19) =32653552a(20) =116866283a(21) =428464743a(22) =1600474365a(23) =6102119282a(24) =23690388631a(25) =93631999867a(26) =376561553417