10000000999domain: NAppears in sequencesFirst prime in primes of the form 10^n + 10^(n-k) - 1.at n=6A096214Primes of the form m = 10^i + 10^j - 1, where i > j >= 0.at n=11A239720Primes of the form 10^i + 10^j - 1.at n=16A306855