359552domain: NAppears in sequencesNumbers with prime signature {7,2}, i.e., of form p^7*q^2 with p and q distinct primes.at n=19A179689Numbers k such that sigma(k) + tau(k) + phi(k) is a prime, where sigma(k) = A000203(k), tau(k) = A000005(k) and phi(k) = A000010(k).at n=33A229265