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A362708
a(n) is the number of almost unitary polyominoes of size n. An almost unitary polyomino is one in which all but 1 of its perimeter walls have length 1.
1
0, 0, 0, 1, 0, 0, 2, 2, 1, 6, 9, 11, 21, 49, 69, 117, 249, 427
OFFSET
1,7
EXAMPLE
a(4)=1 because of:
O
OO
O
CROSSREFS
Sequence in context: A074297 A339604 A020824 * A138678 A335997 A350297
KEYWORD
nonn,hard,more
AUTHOR
John Mason, Apr 30 2023
STATUS
approved