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A123787
Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1x5 which is symmetric after a rotation by 180 degrees.
0
1, 2, 28, 192, 1680, 13644, 118916, 1044873, 9160772
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OFFSET
1,2
LINKS
Table of n, a(n) for n=1..9.
CROSSREFS
Cf.
A112389
,
A123762
-
A123827
,
A123829
-
A123849
.
Sequence in context:
A280120
A065340
A001798
*
A035601
A281124
A244721
Adjacent sequences:
A123784
A123785
A123786
*
A123788
A123789
A123790
KEYWORD
nonn
AUTHOR
Søren Eilers
, Oct 29 2006
STATUS
approved
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Last modified May 7 21:53 EDT 2024. Contains 372317 sequences. (Running on oeis4.)