a(n) = Sum_{i=0..n} T(i,n-i), array T as in A049687.

Terms

a(0) =0a(1) =2a(2) =5a(3) =10a(4) =17a(5) =28a(6) =41a(7) =60a(8) =83a(9) =112a(10) =145a(11) =188a(12) =235a(13) =294a(14) =359a(15) =432a(16) =513a(17) =610a(18) =713a(19) =834a(20) =963a(21) =1104a(22) =1255a(23) =1428a(24) =1609a(25) =1810a(26) =2023a(27) =2254a(28) =2497a(29) =2768