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A144554
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Number of polyominoes with n cells whose symmetry group (excluding reflections) has order at least 2.
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12
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1, 1, 1, 3, 3, 7, 8, 25, 25, 82, 85, 302, 307, 1111, 1131, 4216, 4267, 16076, 16253, 61976, 62475, 239927, 241447, 933576, 937574, 3644073, 3653624, 14267757, 14281711, 55996279, 55968648, 220244340, 219829297, 867868410, 865120447, 3425522409, 3410557920, 13540713898, 13466370893, 53596553368
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OFFSET
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1,4
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COMMENTS
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In other words, a(n) is the number of polyominoes with n cells having at least 180-degree rotational symmetry. - John Mason, Feb 14 2022
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LINKS
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D. H. Redelmeier, Table 3 of Counting polyominoes...
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FORMULA
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MATHEMATICA
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A000105 = Cases[Import["https://oeis.org/A000105/b000105.txt", "Table"], {_, _}][[All, 2]];
A006749 = Cases[Import["https://oeis.org/A006749/b006749.txt", "Table"], {_, _}][[All, 2]];
A006746 = Cases[Import["https://oeis.org/A006746/b006746.txt", "Table"], {_, _}][[All, 2]];
A006748 = Cases[Import["https://oeis.org/A006748/b006748.txt", "Table"], {_, _}][[All, 2]];
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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17 additional terms (just summing the terms from the 5 sequences specified in the description) Fred Schneider, Jan 03 2009
Terms a(37) and beyond from John Mason, Feb 14 2022
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STATUS
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approved
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