

A123823


Number of ways to build a contiguous building with n LEGO blocks of size 2 X 2 on top of a fixed block of the same size so that the building is symmetric after a rotation by 90 degrees.


0



1, 1, 1, 2, 3, 4, 5, 11, 22, 34, 47, 113
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OFFSET

1,4


COMMENTS

The base block is not counted among the n and must be the only block in the bottom layer of the building


LINKS



CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



