168269domain: NPropertiesPrimalityPrimeyesAppears in sequencesNumbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 63.at n=4A031651Primes p such that (p-1)/2 and (p+1)/2 have same sum of divisors.at n=7A171720Prime numbersat n=15358