Duplicate of A000602.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =3a(6) =5a(7) =9a(8) =18a(9) =35a(10) =75a(11) =159a(12) =355a(13) =802a(14) =1858a(15) =4347a(16) =10359a(17) =24894a(18) =60523