a(n) = Sum_{i=0..n} T(i,n-i), array T as in A049727.

Terms

a(0) =1a(1) =4a(2) =9a(3) =16a(4) =26a(5) =38a(6) =56a(7) =74a(8) =101a(9) =130a(10) =167a(11) =204a(12) =260a(13) =306a(14) =374a(15) =446a(16) =525a(17) =604a(18) =715a(19) =808a(20) =942a(21) =1066a(22) =1204a(23) =1346a(24) =1537a(25) =1696a(26) =1891a(27) =2098a(28) =2328a(29) =2538