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A103465
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Number of polyominoes that can be formed from n regular unit pentagons (or polypents of order n).
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13
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1, 1, 2, 7, 25, 118, 551, 2812, 14445, 76092, 403976, 2167116, 11698961, 63544050, 346821209, 1901232614
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,3
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COMMENTS
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Number of 5-polyominoes with n pentagons. A k-polyomino is a non-overlapping union of n regular unit k-gons.
Unlike A051738, these are not anchored polypents but simple polypents. - George Sicherman, Mar 06 2006
Polypents (or 5-polyominoes in Koch and Kurz's terminology) can have holes and this enumeration includes polypents with holes. - George Sicherman, Dec 06 2007
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LINKS
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Table of n, a(n) for n=1..16.
Erich Friedman, Math Magic, September and November 2004.
Matthias Koch and Sascha Kurz, Enumeration of generalized polyominoes (preprint) arXiv:math.CO/0605144
S. Kurz, k-polyominoes.
G. L. Sicherman, Catalogue of Polypents, at Polyform Curiosities.
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EXAMPLE
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a(3)=2 because there are 2 geometrically distinct ways to join 3 regular pentagons edge to edge.
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CROSSREFS
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Cf. A103465, A103466, A103467, A103468, A103469, A103470, A103471, A103472, A103473, A120102, A120103, A120104.
Cf. A000105, A000577, A000228.
Sequence in context: A150535 A076176 A188719 * A103464 A339515 A323658
Adjacent sequences: A103462 A103463 A103464 * A103466 A103467 A103468
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KEYWORD
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more,nonn
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AUTHOR
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Sascha Kurz, Feb 07 2005; definition revised and sequence extended Apr 12 2006 and again Jun 09 2006
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EXTENSIONS
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Entry revised by N. J. A. Sloane, Jun 18 2006
Corrected the dates of the Math Magic pages under "Links." George Sicherman, Nov 08 2009
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STATUS
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approved
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