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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)
 OFFSET 1,3 COMMENTS 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 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 Sascha Kurz, k-polyominoes. George 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 A358498 A339515 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 STATUS approved

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