a(n) = T(n,0) + T(n,1) + ... + T(n,n), T given by A027157.

Terms

a(0) =1a(1) =3a(2) =10a(3) =22a(4) =67a(5) =145a(6) =436a(7) =940a(8) =2821a(9) =6079a(10) =18238a(11) =39298a(12) =117895a(13) =254029a(14) =762088a(15) =1642072a(16) =4926217a(17) =10614523a(18) =31843570a(19) =68613358a(20) =205840075a(21) =443523721a(22) =1330571164a(23) =2866982404a(24) =8600947213a(25) =18532465591a(26) =55597396774