39999999996domain: NAppears in sequencesNumbers n such that 2n+1 is the digit reversal of n+1.at n=9A083811a(n) = 4*(10^n - 1).at n=10A086575a(n) is the smallest k that is equal to the sum of the digits of k*(k+1)*...*(k+n-1) in base 10^n, or -1 if such a number does not exist.at n=9A308408