a(n) = (64^n - 1)/63.A133853a(n) = (64^n - 1)/63.Terms a(0) =0a(1) =1a(2) =65a(3) =4161a(4) =266305a(5) =17043521a(6) =1090785345a(7) =69810262081External referencesoeis: A133853