a(n) = A027113(n, 2n-8).

Terms

a(0) =1a(1) =2a(2) =7a(3) =24a(4) =81a(5) =274a(6) =923a(7) =3087a(8) =10232a(9) =33587a(10) =109190a(11) =351730a(12) =1123465a(13) =3561045a(14) =11210036a(15) =35073033a(16) =109137568a(17) =337969627a(18) =1042129366a(19) =3201226811a(20) =9800475386a(21) =29914121676a(22) =91063951213a(23) =276556071836a(24) =838101477953