A217748 - OEIS

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A217748

Number of regions with infinite area in the exterior of a regular n-gon with all diagonals drawn.

1, 4, 10, 18, 28, 40, 54, 70, 88, 108, 130, 154, 180, 208, 238, 270, 304, 340, 378, 418, 460, 504, 550, 598, 648, 700, 754, 810, 868, 928, 990, 1054, 1120, 1188, 1258, 1330, 1404, 1480, 1558, 1638, 1720, 1804, 1890, 1978, 2068, 2160, 2254, 2350, 2448, 2548 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`3,2`
	COMMENTS	`For n > 3 same as A028552(n-3).`
	LINKS	`Table of n, a(n) for n=3..52.`
	FORMULA	`a(n) = n*(n-3) for n > 3` `a(n) = A217745(n) - A217746(n)`
	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. A004526, A007678, A028552, A164004, A217745, A217746.` `Sequence in context: A161958 A013921 A028552 * A009877 A009880 A197057` `Adjacent sequences: A217745 A217746 A217747 * A217749 A217750 A217751`
	KEYWORD	`nonn`
	AUTHOR	`Martin Renner, Mar 23 2013`
	STATUS	`approved`

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Last modified January 17 00:44 EST 2019. Contains 319206 sequences. (Running on oeis4.)