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A123779
Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1x4 which is symmetric after a rotation by 180 degrees.
0
1, 1, 21, 67, 849, 3185, 39868, 162562, 2027829
OFFSET
1,3
CROSSREFS
KEYWORD
nonn
AUTHOR
Søren Eilers, Oct 29 2006
STATUS
approved