A352144 - OEIS

%I #12 Mar 07 2022 02:39:19

%S 0,1,12,40,140,228,644,1168,1512,3360,5280,6144,11284,15680,13800,

%T 28448,37264,42444,60648,75720,75012,114400,138644,152064,198200,

%U 234208,254988,321048,372708,375060,494140,564800,605352,728960,823480,894816,1039404,1161888,1241760,1439440,1595720

%N 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).

%C 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.

%C See A335102 for images of the 2n-gons.

%H Scott R. Shannon, <a href="/A352144/b352144.txt">Table of n, a(n) for n = 1..72</a>

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

%K nonn

%O 1,3

%A _Scott R. Shannon_ and _N. J. A. Sloane_, Mar 06 2022