10246935931domain: NAppears in sequencesPrimes that are congruent to 1 mod n, where n is the index of the prime.at n=29A048891a(n) is the earliest number m such that n*pi(m)=phi(m).at n=21A097651Primes p that are congruent to 1 mod 2*k, where k = primepi(p) is the index of the prime.at n=20A360277