a(n) = 3^(n - 1) * (9^n - 1) / 8, n >= 1.

A367275

a(n) = 3^(n - 1) * (9^n - 1) / 8, n >= 1.

Terms

    a(0) =1a(1) =30a(2) =819a(3) =22140a(4) =597861a(5) =16142490a(6) =435847959a(7) =11767897080a(8) =317733227721

External references