a(n) = A116648(2^n).

Terms

a(0) =2a(1) =2a(2) =4a(3) =5a(4) =9a(5) =20a(6) =39a(7) =76a(8) =127a(9) =309a(10) =509a(11) =1263a(12) =2621a(13) =5044a(14) =10025