571350096domain: NAppears in sequencesNumber of endofunctions f on [2n] that are self-inverse on [n].at n=6A245141Number A(n,k) of endofunctions f on [2n] satisfying f^k(i) = i for all i in [n]; square array A(n,k), n>=0, k>=0, read by antidiagonals.at n=42A246070