2015330304domain: NAppears in sequencesSum of the divisors of 2^n - 1.at n=29A075708a(0) = 0, a(1) = 1, for n > 1, a(n) = 2^n - (sigma((2^n)-1) - sigma((2^(n-1))-1)).at n=31A329891Sum of the divisors of 4^n-1.at n=14A366603Sum of the divisors of 8^n-1.at n=9A366653