234932757

Appears in sequences

• Half the number of n X n symmetric binary matrices with every 1 adjacent to some 0 horizontally or vertically and every 0 adjacent to some 1 horizontally or vertically.at n=6A140422
• T(n,k) = Half the number of lower triangles of an (n+1) X (n+1) 0..k array with no element equal to the average of its horizontal and vertical neighbors.at n=27A194615