a(n) = A024727(n+3)/4.

Terms

a(0) =1a(1) =1a(2) =1a(3) =5a(4) =9a(5) =13a(6) =33a(7) =73a(8) =145a(9) =313a(10) =657a(11) =1549a(12) =3353a(13) =7221a(14) =16129a(15) =36785a(16) =81921a(17) =180529a(18) =403809a(19) =939573a(20) =2125193a(21) =4756893a(22) =10800801a(23) =25195577a(24) =57552721a(25) =130500393a(26) =298271153a(27) =700076797a(28) =1610366937a(29) =3680601093