A123837 - OEIS

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A123837

Number of ways to build a contiguous building with n LEGO blocks of size 3 X 3 on top of a fixed block of the same size so that the building is symmetric after a rotation by 90 degrees.

1, 1, 1, 4, 7, 10, 13, 61, 154, 256 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`1,4`
	COMMENTS	`The base block is not counted among the n and must be the only block in the bottom layer of the building`
	LINKS	`Table of n, a(n) for n=1..10.`
	CROSSREFS	`Cf. A112389, A123762 - A123827, A123829 - A123849.` `Sequence in context: A119256 A143454 A065810 * A125620 A062389 A191402` `Adjacent sequences: A123834 A123835 A123836 * A123838 A123839 A123840`
	KEYWORD	`nonn`
	AUTHOR	`Soren Eilers (eilers(AT)math.ku.dk), Oct 29 2006`
	STATUS	`approved`

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Last modified May 25 21:30 EDT 2013. Contains 225649 sequences.