6124032

Appears in sequences

• Number of one-to-one functions f from [n] to [2n] where f(x) may not be equal to x or to 2n+1-x.at n=7A272261
• Number of ways to select four points from an n X n grid so that three of them form a triangle of nonzero area and the extra point is on one of the edges of the triangle.at n=14A334713