a(n) = Sum_{i=0..n} Sum_{j=i..2*i} A027052(i, j).

Terms

a(0) =1a(1) =2a(2) =6a(3) =16a(4) =43a(5) =120a(6) =340a(7) =972a(8) =2793a(9) =8050a(10) =23256a(11) =67324a(12) =195275a(13) =567448a(14) =1651830a(15) =4816328a(16) =14064569a(17) =41128626a(18) =120425604a(19) =353022920a(20) =1035983443a(21) =3043189688a(22) =8947381566a(23) =26328236756a(24) =77531471737a(25) =228475334594a(26) =673725464150