224911domain: NPropertiesPrimalityPrimeyesAppears in sequencesIrregular primes the indices of whose indices are irregular primes of order two.at n=19A090887a(n) = 10*a(n-1)-19*a(n-2) for n > 1; a(0) = 1, a(1) = 9.at n=6A164551Prime numbersat n=20013