1860277042domain: NAppears in sequencesa(n) = [ C(2n,n)/n ].at n=18A024498Number of orbits of length n under the map whose periodic points are counted by A000984.at n=18A060165Erroneous version of A177454.at n=6A078464a(n) = (binomial(2*p,p) - 2)/p, where p = prime(n).at n=7A177454