1748803domain: NAppears in sequencesTriangle read by rows: T(n,k) (1 <= k <= n) = number of irreducible coverings by edges of the complete bipartite graph K_{n,k}.at n=27A210654Number of irreducible coverings by edges of the complete bipartite graph K_{n,n}; main diagonal of A210654.at n=6A210655