a(n) = T(n, 2*n-6), T given by A027926.

Terms

a(0) =1a(1) =2a(2) =5a(3) =13a(4) =33a(5) =79a(6) =176a(7) =365a(8) =709a(9) =1300a(10) =2267a(11) =3785a(12) =6085a(13) =9465a(14) =14302a(15) =21065a(16) =30329a(17) =42790a(18) =59281a(19) =80789a(20) =108473a(21) =143683a(22) =187980a(23) =243157a(24) =311261a(25) =394616a(26) =495847a(27) =617905a(28) =764093a(29) =938093