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

1,4

Comments

A non-degenerate parallelogram has positive area.

Links

Christopher N. Swanson, Randy Ho, and Bill Correll, Jr., Table of n, a(n) for n = 1..1000

Mathematics Stack Exchange, Counting non-degenerate parallelograms in permutation arrays

Crossrefs

Sequence in context: A271968 A022502 A272956 * A200803 A198965 A342959

Adjacent sequences: A243640 A243641 A243642 * A243644 A243645 A243646

Keyword

nonn

Author

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

Status

approved