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A123817 Number of ways to build a contiguous building with n LEGO blocks of size 1 X 8 on top of a fixed block of the same size so that the building is flat, i.e., with all blocks in parallel position and symmetric after a rotation by 180 degrees. 0
1, 5, 9, 51, 131, 807, 2129, 13967, 39701, 265152 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

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.

Index entry for sequences related to LEGO blocks

CROSSREFS

Cf. A112389, A123762 - A123827, A123829 - A123849.

Sequence in context: A173776 A289909 A000324 * A124421 A262918 A283918

Adjacent sequences:  A123814 A123815 A123816 * A123818 A123819 A123820

KEYWORD

nonn

AUTHOR

Søren Eilers, Oct 29 2006

STATUS

approved

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Last modified February 23 09:52 EST 2018. Contains 299535 sequences. (Running on oeis4.)