a(n) = A027082(n, n+3).

Terms

a(0) =5a(1) =16a(2) =39a(3) =84a(4) =169a(5) =328a(6) =623a(7) =1168a(8) =2173a(9) =4024a(10) =7431a(11) =13700a(12) =25233a(13) =46448a(14) =85471a(15) =157248a(16) =289269a(17) =532096a(18) =978727a(19) =1800212a(20) =3311161a(21) =6090232a(22) =11201743a(23) =20603280a(24) =37895405a(25) =69700584a(26) =128199431a(27) =235795588a(28) =433695777a(29) =797690976