a(n) = A027113(n, 2n-9).

Terms

a(0) =1a(1) =4a(2) =13a(3) =44a(4) =149a(5) =504a(6) =1701a(7) =5715a(8) =19079a(9) =63218a(10) =207803a(11) =677598a(12) =2192383a(13) =7041688a(14) =22463815a(15) =71216406a(16) =224495351a(17) =704036264a(18) =2197641219a(19) =6831066997a(20) =21152812449a(21) =65276358340a(22) =200814955029a(23) =616052453764