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A123821
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.
0
9, 97, 1349, 20288, 329707, 5574248, 97506021, 1747201171, 31923371982, 592403479154
OFFSET
1,1
COMMENTS
The base block is not counted among the n and must be the only block in the bottom layer of the building
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Søren Eilers, Oct 29 2006
STATUS
approved