159822domain: NAppears in sequencesa(n) = Sum_{k=0..floor(n/3)} (binomial(n+1, k)*binomial(2*n-3*k, n-3*k)/(n+1)).at n=11A071969Duplicate of A071969.at n=11A119255Number of forests of labeled rooted trees of height at most 1, with n labels, two of which are used for root nodes and any root may contain >= 1 labels.at n=11A273652