438750domain: NAppears in sequencesNumber of tree-rooted planar maps with 3 faces and n vertices and no isthmuses.at n=23A006470a(n) = n*(n-1)*(n-2)^2.at n=25A047927Number of arrangements of n indistinguishable balls in n boxes with the maximum number of balls in any box equal to n-4.at n=20A180294