a(n) = A216958(n)/2.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =5a(5) =10a(6) =18a(7) =36a(8) =71a(9) =140a(10) =280a(11) =557a(12) =1111a(13) =2218a(14) =4432a(15) =8859a(16) =17710a(17) =35412a(18) =70812a(19) =141605a(20) =283197a(21) =566364a(22) =1132695a(23) =2265363a(24) =4530659a(25) =9061259a(26) =18122454a(27) =36244783a(28) =72489435a(29) =144978745