a(n) = round(Product_{k=1..n} (1 + 1/2^2^(-k))).

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =12a(5) =23a(6) =46a(7) =93a(8) =185a(9) =370a(10) =739a(11) =1478a(12) =2955a(13) =5910a(14) =11819a(15) =23637a(16) =47274a(17) =94549a(18) =189097a(19) =378194a(20) =756388a(21) =1512776a(22) =3025551a(23) =6051102a(24) =12102203a(25) =24204407a(26) =48408813a(27) =96817626a(28) =193635251a(29) =387270501