a(n) = [x^n] Product_{k>=0} 1/(1 - x^(2^k))^n.

Terms

a(0) =1a(1) =1a(2) =5a(3) =19a(4) =89a(5) =401a(6) =1877a(7) =8821a(8) =41969a(9) =200899a(10) =967605a(11) =4681491a(12) =22739705a(13) =110816343a(14) =541561333a(15) =2653061819a(16) =13024808161a(17) =64063300481a(18) =315624211781