a(0) = 0, a(n) = Sum_{i=0..n-1} 2^((2^i)-1).
A072639
a(0) = 0, a(n) = Sum_{i=0..n-1} 2^((2^i)-1).
Terms
- a(0) =0a(1) =1a(2) =3a(3) =11a(4) =139a(5) =32907a(6) =2147516555
External references
- oeis: A072639
A072639
a(0) = 0, a(n) = Sum_{i=0..n-1} 2^((2^i)-1).