221738

Appears in sequences

• Triangle T(n,k), n>=1, 0 <= k <= A002620(n-1), read by rows, where T(n,k) is the number of self-avoiding paths of length 2*(n+k) along the edges of a grid with n X n square cells, which do not pass above the diagonal, start at the lower left corner and finish at the upper right corner.at n=40A340043
• Number of n-celled polytans with holes.at n=13A350580