280221

Appears in sequences

• Number of words on {1,1,2,2,3,3,...,n,n} avoiding the pattern 123.at n=7A220097
• Number A(n,k) of words on {1,1,2,2,...,n,n} with longest increasing subsequence of length <= k; square array A(n,k), n>=0, k>=0, read by antidiagonals.at n=52A267479