56409643domain: NPropertiesPrimalityPrimeyesAppears in sequencesSmallest primitive factor of 2^(2n+1) + 1.at n=35A002185Smallest prime factor of the n-th Jacobsthal number: a(n) = A020639(A001045(n)), with a(1)=a(2)=1.at n=70A286567Smallest prime factor of (2^prime(n) + 1) / 3.at n=18A360475Prime numbersat n=3361308