a(n) = Sum_{i=0..n} binomial(2^n-1, i).

A046855

a(n) = Sum_{i=0..n} binomial(2^n-1, i).

Terms

    a(0) =1a(1) =2a(2) =7a(3) =64a(4) =1941a(5) =206368a(6) =75611761a(7) =94790703104

External references