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A128115

Mobius inversion of A103221.

0, 1, 0, 0, 1, 0, 1, 1, 1, 0, 2, 1, 2, 1, 1, 1, 3, 1, 3, 2, 2, 1, 4, 1, 3, 2, 3, 2, 5, 2, 5, 3, 3, 2, 4, 2, 6, 3, 4, 2, 7, 2, 7, 4, 4, 3, 8, 3, 7, 4, 5, 4, 9, 3, 6, 4, 6, 4, 10, 2, 10, 5, 6, 5, 8, 4, 11, 6, 7, 4, 12, 4, 12, 6, 7, 6, 10, 4, 13, 6, 9, 6, 14, 4, 10, 7, 9, 6, 15, 4, 12, 8, 10, 7, 12, 5, 16, 7 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`1,11`
	COMMENTS	`Number of uniform n-grammic crossed antiprisms.` `Agrees with Mobius inversion of A008615 for n != 3. - Andrew Baxter, Jun 06 2008` `Number of primitive equivalence classes of period 2n billiards on an equilateral triangle. - Andrew Baxter, Jun 06 2008`
	LINKS	`Table of n, a(n) for n=1..98.` `Andrew M. Baxter and Ron Umble, Periodic Orbits of Billiards on an Equilateral Triangle, Amer. Math. Monthly, 115 (No. 6, 2008), 479-491.`
	FORMULA	`SUM_{d\|n} mu(d) * A103221(n/d), where mu is Mobius function (A008683). - Andrew Baxter, Jun 06 2008`
	MAPLE	`with(numtheory): A103221:=n->floor((n+2)/2)-floor((n+2)/3): A128115:=n->add(mobius(d)*A103221(n/d), d in divisors(n)): # Andrew Baxter, Jun 06 2008`
	CROSSREFS	`Cf. A055684.` `Cf. A008615, A103221.` `Sequence in context: A145672 A175024 A175023 * A091318 A198898 A003639` `Adjacent sequences: A128112 A128113 A128114 * A128116 A128117 A128118`
	KEYWORD	`nonn`
	AUTHOR	`Paulo de Almeida Sachs (sachs6(AT)yahoo.de), Feb 15 2007`
	EXTENSIONS	`Edited by Andrew Baxter, Jun 06 2008`
	STATUS	`approved`

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Last modified August 2 17:23 EDT 2024. Contains 374848 sequences. (Running on oeis4.)