a(n) = 2 * Sum_{i=0..n} C(2^n-1, i).
A001527
a(n) = 2 * Sum_{i=0..n} C(2^n-1, i).
Terms
- a(0) =2a(1) =4a(2) =14a(3) =128a(4) =3882a(5) =412736a(6) =151223522a(7) =189581406208
External references
- oeis: A001527
A001527
a(n) = 2 * Sum_{i=0..n} C(2^n-1, i).