1009999999domain: NAppears in sequencesPrimes of the form 10^n + 10^(n-2) - 1.at n=3A096210Primes of the form m = 10^i + 10^j - 1, where i > j >= 0.at n=10A239720Primes of the form 10^i + 10^j - 1.at n=15A306855