990000000000domain: NAppears in sequences10^n-10^(n-2).at n=12A105694Total number of digits in all n-digit nonnegative integers.at n=10A113119a(n) = 9*n*10^(n-1).at n=10A212704Number of strings of k+n decimal digits that contain one string of exactly k consecutive "0" digits, where k >= n.at n=11A255381