a(n) = Product_{k=1..n-1} (ceiling(n/k) - ceiling(n/k) mod 2).

Terms

a(0) =1a(1) =2a(2) =4a(3) =16a(4) =32a(5) =96a(6) =384a(7) =1024a(8) =2048a(9) =10240a(10) =30720a(11) =73728a(12) =294912a(13) =688128a(14) =1835008a(15) =12582912a(16) =25165824a(17) =56623104a(18) =283115520a(19) =629145600a(20) =1887436800a(21) =11072962560a(22) =26575110144a(23) =57982058496a(24) =231928233984a(25) =753766760448