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A123815 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 symmetric after a rotation by 180 degrees. 0
1, 37, 73, 2995, 9235, 404559, 1360441 (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..7.

CROSSREFS

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

Sequence in context: A146241 A217386 A083990 * A289732 A087531 A283718

Adjacent sequences:  A123812 A123813 A123814 * A123816 A123817 A123818

KEYWORD

nonn,more

AUTHOR

Søren Eilers, Oct 29 2006

STATUS

approved

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Last modified February 16 21:59 EST 2019. Contains 320200 sequences. (Running on oeis4.)