142793domain: NAppears in sequencesSymmetries in planted 3-trees on n+1 vertices.at n=16A003611a(n) = 1 + Sum_{k=1..n-3} a(k) * a(n-k-3).at n=26A346075Number of distinct subsets S of [n] such that for all 1 <= k <= n, there exist elements x,y in S (not necessarily distinct) such that x*y = 2k.at n=27A384330