a(1) = 1, a(n) = Sum_{k=1..n-1} ((4^k - 1)/3)*a(k).
A015503
a(1) = 1, a(n) = Sum_{k=1..n-1} ((4^k - 1)/3)*a(k).
Terms
- a(0) =1a(1) =1a(2) =6a(3) =132a(4) =11352a(5) =3882384a(6) =5303336544
External references
- oeis: A015503
A015503
a(1) = 1, a(n) = Sum_{k=1..n-1} ((4^k - 1)/3)*a(k).