

A103465


Number of polyominoes that can be formed from n regular unit pentagons (or polypents of order n).


12



1, 1, 2, 7, 25, 118, 551, 2812, 14445, 76092, 403976, 2167116, 11698961, 63544050, 346821209, 1901232614
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OFFSET

1,3


COMMENTS

Number of 5polyominoes with n pentagons. A kpolyomino is a nonoverlapping union of n regular unit kgons.
Unlike A051738, these are not anchored polypents but simple polypents.  George Sicherman, Mar 06 2006
Polypents (or 5polyominoes in Koch and Kurz's terminology) can have holes and this enumeration includes polypents with holes.  George Sicherman, Dec 06 2007


LINKS

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, kpolyominoes.
G. L. Sicherman, Catalogue of Polypents, at Polyform Curiosities.


EXAMPLE

a(3)=2 because there are 2 geometrically distinct ways to join 3 regular pentagons edge to edge.


CROSSREFS

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


KEYWORD

more,nonn


AUTHOR

Sascha Kurz, Feb 07 2005; definition revised and sequence extended Apr 12 2006 and again Jun 09 2006


EXTENSIONS

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


STATUS

approved



