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A146213 Draw lines through the vertices of a regular n-gon. a(n) is the number of intersection points outside of the n-gon. 3
0, 0, 5, 18, 49, 88, 198, 300, 550, 588, 1235, 1414, 2415, 2576, 4284, 3708, 7068, 7280, 11025, 11330, 16445, 14592, 23650, 23972, 32994, 33208, 44863, 34830, 59675, 59808, 77880, 78064, 99960, 92844, 126429, 126426, 157833, 157560, 194750 (list; graph; refs; listen; history; text; internal format)
OFFSET
3,3
COMMENTS
Note that n divides a(n). For odd n, it appears that a(n)=n(2n^3-15^2+34n-21)/24.
LINKS
FORMULA
a(n) = A146212(n) - A007569(n).
CROSSREFS
Sequence in context: A256539 A109363 A218214 * A344311 A176145 A270978
KEYWORD
nonn
AUTHOR
T. D. Noe, Oct 28 2008
EXTENSIONS
More terms from Jon E. Schoenfield, Nov 11 2008
STATUS
approved

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Last modified March 28 22:04 EDT 2024. Contains 371254 sequences. (Running on oeis4.)