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A341219
Number of well-connected free polyominoes with n cells, where a polyomino is defined as well-connected if, for all the squares it contains, the removal of that single square would result in an intact polyomino.
2
1, 1, 1, 0, 1, 0, 1, 0, 3, 1, 6, 2, 25, 18, 88
OFFSET
0,9
COMMENTS
Examples of well-connected polyominoes are rectangles and loops:
.
XXXX
XXXX (rectangle)
.
XXX
X X (loop)
XXX
EXAMPLE
a(4) = 1 because the 2 X 2 square polyomino is the only tetromino to be well-connected. The removal of any single square always results in an intact tromino. In each of the other 4 tetrominoes, there is a square whose removal would result in something that is not an intact polyomino.
CROSSREFS
Cf. A000105.
Sequence in context: A322387 A336173 A072361 * A145366 A145367 A124928
KEYWORD
nonn,more
AUTHOR
John Mason, Feb 07 2021
STATUS
approved