A011946 - OEIS

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A011946

Number of Barlow packings with group P63/mmc(S) that repeat after 4n layers.

1, 2, 3, 8, 15, 30, 63, 128, 252, 510, 1023, 2040 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,2`
	LINKS	`T. J. McLarnan, The numbers of polytypes in close packings and related structures, Zeits. Krist. 155, 269-291 (1981).`
	FORMULA	`Conjecture: a(n) = nfloor(2^n/(2n)). - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Apr 02 2007`
	CROSSREFS	`Cf. A195095.` `Sequence in context: A099428 A099920 A128022 * A195095 A166920 A080206` `Adjacent sequences: A011943 A011944 A011945 * A011947 A011948 A011949`
	KEYWORD	`nonn,easy`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com).`

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Last modified February 17 16:38 EST 2012. Contains 206058 sequences.