66949domain: NPropertiesPrimalityPrimeyesAppears in sequencesNumbers k such that 10^k - 9^k is prime.at n=10A062576Primes having only {4, 6, 9} as digits.at n=21A107666a(n) is the smallest number whose sum with any previous term is abundant.at n=8A383398Prime numbersat n=6672