a(n) = Product_{k=1..n} d(2*k - 1), where d() is the number of divisors function A000005.

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =24a(5) =48a(6) =96a(7) =384a(8) =768a(9) =1536a(10) =6144a(11) =12288a(12) =36864a(13) =147456a(14) =294912a(15) =589824a(16) =2359296a(17) =9437184a(18) =18874368a(19) =75497472a(20) =150994944a(21) =301989888a(22) =1811939328a(23) =3623878656a(24) =10871635968a(25) =43486543872a(26) =86973087744a(27) =347892350976