a(n) = T(n, 2*n-7), T given by A027960.

Terms

a(0) =3a(1) =7a(2) =18a(3) =47a(4) =120a(5) =291a(6) =661a(7) =1404a(8) =2801a(9) =5283a(10) =9484a(11) =16305a(12) =26990a(13) =43215a(14) =67191a(15) =101782a(16) =150639a(17) =218351a(18) =310614a(19) =434419a(20) =598260a(21) =812363a(22) =1088937a(23) =1442448a(24) =1889917a(25) =2451243a(26) =3149552a(27) =4011573a(28) =5068042a(29) =6354135