17399772domain: NAppears in sequencesa(n) = 2*3^n*(2*n)!/(n!*(n+2)!).at n=9A000168Triangle T(n,k) read by rows: T(n,k) is the number of rooted genus-k maps with n edges, n>=0, 0<=k<=n.at n=45A238396Triangle read by rows: T(n,g) is the number of rooted maps with n edges on an orientable surface of genus g.at n=25A269919