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Search: id:A137191
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| A137191 |
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Number of n-celled polyiamonds with perimeter < n+2. |
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+0
1
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| 0, 0, 0, 0, 0, 1, 1, 4, 11, 39, 120, 403, 1254, 4000, 12475, 39030
(list; graph; listen)
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OFFSET
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1,8
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COMMENT
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These are n-cell polyiamonds with the perimeter less than the maximum possible one.
If we associate a graph to a polyiamond with vertices representing cells and edges representing two cells with a common edge, then this sequence enumerates polyiamonds whose corresponding graphs have cycles.
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FORMULA
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A000577(n) - A131481(n)
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CROSSREFS
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Sequence in context: A149256 A149257 A050987 this_sequence A106269 A126758 A149258
Adjacent sequences: A137188 A137189 A137190 this_sequence A137192 A137193 A137194
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KEYWORD
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hard,more,nonn
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AUTHOR
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Tanya Khovanova (tanyakh(AT)yahoo.com), Mar 03 2008
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