a(n) = Sum_{0<=i<=i<=n} A027082(i, n+j).

Terms

a(0) =1a(1) =3a(2) =9a(3) =28a(4) =83a(5) =244a(6) =713a(7) =2075a(8) =6029a(9) =17512a(10) =50891a(11) =148037a(12) =431151a(13) =1257365a(14) =3671731a(15) =10735948a(16) =31429745a(17) =92116592a(18) =270268647a(19) =793741973a(20) =2333221387a(21) =6864280611a(22) =20210115899a(23) =59545932370a(24) =175558633893a(25) =517915132777