A243643 Number of non-degenerate parallelograms in an n X n permutation array.

0, 0, 0, 6, 62, 362, 1266, 3692, 8904, 19376, 38144, 70574, 122478, 203722, 324554, 500868, 749128, 1094204, 1560240, 2183562, 2998598, 4055502, 5402450, 7107528, 9233488, 11870016, 15100040, 19037586, 23787678, 29495558, 36290898, 44354248, 53846392, 64985376

Offset: 1

Author

Christopher N. Swanson, Randy Ho, Bill Correll, Jr., Jun 08 2014

Keywords

• nonn

Comments

A non-degenerate parallelogram has positive area.

Links

• Christopher N. Swanson, Randy Ho, Bill Correll, Jr., Table of n, a(n) for n = 1..1000
• Mathematics Stack Exchange, Counting non-degenerate parallelograms in permutation arrays