a(n) = T(n+1,n), array T given by A048201.

Terms

a(0) =2a(1) =6a(2) =11a(3) =19a(4) =29a(5) =43a(6) =58a(7) =74a(8) =95a(9) =117a(10) =142a(11) =168a(12) =196a(13) =229a(14) =263a(15) =298a(16) =334a(17) =372a(18) =412a(19) =454a(20) =500a(21) =548a(22) =597a(23) =647a(24) =700a(25) =757a(26) =817a(27) =879a(28) =943a(29) =1008