A352144 The number of interior points that are intersections of exactly two chords for a 2n-gon where all its vertices are joined by lines (cf. A006561).

0, 1, 12, 40, 140, 228, 644, 1168, 1512, 3360, 5280, 6144, 11284, 15680, 13800, 28448, 37264, 42444, 60648, 75720, 75012, 114400, 138644, 152064, 198200, 234208, 254988, 321048, 372708, 375060, 494140, 564800, 605352, 728960, 823480, 894816, 1039404, 1161888, 1241760, 1439440, 1595720

Offset

1,3

Comments

For the (2n+1)-gon the number of interior simple intersections is given by binomial(n,4) as all interior points are simple. For the 2n-gon, this sequence, no such formula is currently known.

See A335102 for images of the 2n-gons.

Links

Scott R. Shannon, Table of n, a(n) for n = 1..72

Crossrefs

Cf. A292104 (all n-gons), A006561, A335102.

Sequence in context: A320252 A350124 A359566 * A180093 A137389 A228203

Adjacent sequences: A352141 A352142 A352143 * A352145 A352146 A352147

Keyword

nonn

Author

Scott R. Shannon and N. J. A. Sloane, Mar 06 2022

Status

approved