OFFSET
0,3
LINKS
John Mason, Table of n, a(n) for n = 0..1000
John Mason, Counting free tilings of a rectangle
FORMULA
EXAMPLE
a(4) is 6 because of:
+-+-+-+ +-+-+-+ +-+-+-+ +-+-+-+ +-+-+-+ +-+-+-+
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+-+-+-+ + + + +-+ + +-+ + +-+ +-+-+-+
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+-+-+-+ + + +-+-+-+ +-+-+-+ +-+-+-+ + +-+
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+-+-+-+ +-+-+-+ + +-+ +-+ + +-+-+-+ +-+-+-+
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+-+-+-+ +-+-+-+ +-+-+-+ +-+-+-+ +-+-+-+ +-+-+-+
CROSSREFS
KEYWORD
nonn
AUTHOR
John Mason, Dec 12 2022
STATUS
approved