4106680

Appears in sequences

• Number of permutations of 2 copies of 1..n introduced in order 1..n with no element equal to another within a distance of 2.at n=9A190823
• Triangle read by rows: T(n,k) = number of linear chord diagrams with n chords such that every chord has length at least k (1 <= k <= n).at n=38A293157