31558domain: NAppears in sequencesNumber of matchings in the n-sun graph.at n=8A192856Number of monoids of order n that are not groups.at n=7A320420Start the sequence S with a(1) = 1008973 and extend S with a(n)/2 when a(n) is even, otherwise with a(n) + the smallest prime not yet added.at n=12A388141