36680domain: NAppears in sequencesNumbers k such that k^2 + 1 = p*q, p and q primes and |p-q| is square.at n=43A187401Numbers k such that k^2 + 1 = p*q, p < q primes and q-p is a power of 2.at n=4A238947a(n) is the least k such that k^2 + 1 is a semiprime p*q, p < q, and (q - p)/2^n is prime.at n=13A258780