222953domain: 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 72.at n=5A031660Primes of the form 16*m^2 + 169, m=1,2,3,...at n=30A087862Primes of the form 232*m^2+1.at n=20A230392Prime numbersat n=19853