Column of Motzkin triangle.

Terms

a(0) =1a(1) =6a(2) =27a(3) =104a(4) =369a(5) =1242a(6) =4037a(7) =12804a(8) =39897a(9) =122694a(10) =373581a(11) =1128816a(12) =3390582a(13) =10136556a(14) =30192102a(15) =89662216a(16) =265640691a(17) =785509362a(18) =2319218869a(19) =6839057544a(20) =20147488020a(21) =59306494520a(22) =174466248840a(23) =512987904000