

A217745


Number of regions in the exterior of a regular ngon with all diagonals drawn.


3



1, 4, 10, 18, 35, 64, 117, 190, 330, 492, 780, 1050, 1605, 2080, 2941
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OFFSET

3,2


LINKS



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



KEYWORD

nonn


AUTHOR



STATUS

approved



