102030

Appears in sequences

• Number of forests of ordered trees on n total nodes.at n=12A052854
• Number T(n,k) of permutations of [n] with exactly k (possibly overlapping) occurrences of the consecutive step pattern up, down, up; triangle T(n,k), n>=0, 0<=k<=max(0,floor(n/2)-1), read by rows.at n=20A227884