a(n) = 2^(n^2 + 2n + 1)*Product_{j=1..n} (4^j - 1).

A090770

a(n) = 2^(n^2 + 2n + 1)*Product_{j=1..n} (4^j - 1).

Terms

    a(0) =2a(1) =48a(2) =23040a(3) =185794560

External references