1105335

Appears in sequences

• Number of unlabeled planar trees (also called plane trees) with n nodes.at n=17A002995
• Triangle T(n, k) read by rows; given by [1, 2, 3, 4, 5, 6, ..] DELTA [1, 4, 9, 16, 25, 36, ...] where DELTA is the operator defined in A084938.at n=23A086872
• Number of symmetric difference-closed 4-sets consisting of sets consisting of an even number of pairwise disjoint 2-subsets of {1,2,...,n}.at n=11A266503