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

A028368

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

Terms

    a(0) =1a(1) =2a(2) =8a(3) =192a(4) =21504a(5) =10321920a(6) =20478689280

External references