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A103465 Number of polyominoes that can be formed from n regular unit pentagons (or polypents of order n). 13
1, 1, 2, 7, 25, 118, 551, 2812, 14445, 76092, 403976, 2167116, 11698961, 63544050, 346821209, 1901232614 (list; graph; refs; listen; history; text; internal format)
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
Erich Friedman, Math Magic, September and November 2004.
Matthias Koch and Sascha Kurz, Enumeration of generalized polyominoes (preprint) arXiv:math.CO/0605144
Sascha Kurz, k-polyominoes.
George Sicherman, Catalogue of Polypents, at Polyform Curiosities.
a(3)=2 because there are 2 geometrically distinct ways to join 3 regular pentagons edge to edge.
Sequence in context: A150535 A076176 A188719 * A103464 A358498 A339515
Sascha Kurz, Feb 07 2005; definition revised and sequence extended Apr 12 2006 and again Jun 09 2006
Entry revised by N. J. A. Sloane, Jun 18 2006

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Last modified December 4 10:17 EST 2023. Contains 367560 sequences. (Running on oeis4.)