a(n) = (4^(3*n+2) - 7)/9.

A350054

a(n) = (4^(3*n+2) - 7)/9.

Terms

    a(0) =113a(1) =7281a(2) =466033a(3) =29826161a(4) =1908874353a(5) =122167958641

External references