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A217745 Number of regions in the exterior of a regular n-gon with all diagonals drawn. 3
1, 4, 10, 18, 35, 64, 117, 190, 330, 492, 780, 1050, 1605, 2080, 2941 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,2

LINKS

Table of n, a(n) for n=3..17.

EXAMPLE

a(3) = 1 since the equilateral triangle has no diagonals and therefore one exterior region (with infinite area).

a(4) = 4 since the two diagonals of the square divide the exterior in four regions (with infinite area).

a(5) = 10 since the ten diagonals of the regular pentagon divide the exterior in ten regions (with infinite area) of two different shapes.

CROSSREFS

Cf. A007678.

Sequence in context: A050188 A062361 A038416 * A213949 A009913 A063591

Adjacent sequences:  A217742 A217743 A217744 * A217746 A217747 A217748

KEYWORD

nonn

AUTHOR

Martin Renner, Mar 23 2013

STATUS

approved

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Last modified January 24 16:32 EST 2020. Contains 331204 sequences. (Running on oeis4.)