Duplicate of A000786.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =6a(5) =11a(6) =19a(7) =33a(8) =55a(9) =95a(10) =158a(11) =267a(12) =442a(13) =731a(14) =1193a(15) =1947a(16) =3137a(17) =5039a(18) =8026