Sum of the divisors of 9^n-1.

Terms

a(0) =15a(1) =186a(2) =1680a(3) =15876a(4) =123690a(5) =1541568a(6) =8992680a(7) =111757968a(8) =967814400a(9) =9366647892a(10) =62424587520a(11) =852903426816