a(n) = Sum{T(n,k-1), k = 1,2,...,n}.

Terms

a(0) =1a(1) =3a(2) =8a(3) =23a(4) =67a(5) =197a(6) =582a(7) =1725a(8) =5124a(9) =15245a(10) =45412a(11) =135401a(12) =404015a(13) =1206247a(14) =3603230a(15) =10767855a(16) =32189931a(17) =96259221a(18) =287924196a(19) =861415809a(20) =2577711045a(21) =7714933851a(22) =23093949534a(23) =69139301043a(24) =207017139906a(25) =619921659303