6249100domain: NAppears in sequencesa(n) = lcm{1, ..., 2n} / binomial(2n, n).at n=26A068550Central terms of the triangle A182579.at n=18A182584a(n) = [x^n] (1 + x)/(1 - x)^(2*n+1).at n=9A227726Number of preferential arrangements of n labeled elements such that the minimal number of elements per rank equals 9.at n=17A245862