237379domain: NPropertiesPrimalityPrimeyesAppears in sequencesNumbers k such that 2^(k-1) == 1 + b*k (mod k^2), where b divides k - 2^p for some integer p >= 0 and 2^p <= b.at n=56A186884Meandric numbers for a river crossing up to 7 parallel roads at n points.at n=14A208453Prime numbersat n=21015