a(n) = A027082(n, 2n-9).

Terms

a(0) =1a(1) =3a(2) =9a(3) =31a(4) =105a(5) =355a(6) =1198a(7) =4024a(8) =13429a(9) =44479a(10) =146145a(11) =476347a(12) =1540615a(13) =4946425a(14) =15774197a(15) =49992571a(16) =157545775a(17) =493946713a(18) =1541481630a(19) =4790452228a(20) =14831036177a(21) =45759663403a(22) =140751744489a(23) =431730577935