162030637440domain: NAppears in sequencesNumber of circular permutations of the multiset {1,1,2,2,...,n,n} (up to rotations) with even distances between equal elements.at n=9A137737Number of circular permutations of the multiset {1,1,2,2,...,2n,2n} (up to rotations) with even distances between equal elements.at n=4A137749