99599domain: NAppears in sequencesNumbers having four 9's in base 10.at n=23A043528Largest palindrome using minimum number of digits with a digit sum = n.at n=41A070244Near-repdigit semiprimes with 9 as repeated digit.at n=37A105990Numerator of 24*Stirling_2(n,4)/n!.at n=15A324003a(n) = 10^(2*n+1) - 4*10^n - 1.at n=2A332195