2172830domain: NAppears in sequencesMeandric numbers: number of ways a river can cross a road n times.at n=18A005316Number of meanders in which first bridge is 3.at n=17A006660Meandric numbers for a river crossing two parallel roads at n points.at n=17A076876Number of ways a river can cross a road 2n times.at n=9A077054