a(n) = tau(binomial(2*n,n)), where tau = number of divisors (A000005).

Terms

a(0) =1a(1) =2a(2) =4a(3) =6a(4) =8a(5) =18a(6) =24a(7) =32a(8) =48a(9) =48a(10) =48a(11) =128a(12) =96a(13) =192a(14) =384a(15) =480a(16) =384a(17) =768a(18) =1152a(19) =1536a(20) =2304a(21) =2048a(22) =2048a(23) =3840a(24) =3456a(25) =4608a(26) =6144a(27) =3840a(28) =8192a(29) =20480