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A123819 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 2 X 2 which is symmetric after a rotation by 180 degrees. 0
1, 1, 5, 8, 65, 126, 1023, 2187, 17585, 39606, 315326, 737302 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..12.

CROSSREFS

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

Sequence in context: A132050 A250067 A213239 * A286076 A302651 A260695

Adjacent sequences:  A123816 A123817 A123818 * A123820 A123821 A123822

KEYWORD

nonn

AUTHOR

Søren Eilers, Oct 29 2006

STATUS

approved

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Last modified March 18 17:51 EDT 2019. Contains 321292 sequences. (Running on oeis4.)