a(n) = (2^n / n!) * (2^1 - 1) * (2^2 - 1) * ... * (2^n - 1).

A305627

a(n) = (2^n / n!) * (2^1 - 1) * (2^2 - 1) * ... * (2^n - 1).

Terms

    a(0) =1a(1) =2a(2) =6a(3) =28a(4) =210a(5) =2604a(6) =54684a(7) =1984248a(8) =126495810a(9) =14364301980

External references