4023737domain: NPropertiesPrimalityPrimeyesAppears in sequencesLargest prime substring in n! (0 if none).at n=18A046277a(n) = a(n-1) + 5*a(n-2) for n >= 2, a(0)=1, a(1)=2.at n=15A133407Prime numbersat n=284720