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 A289191 Number of polygonal tiles with n sides with two exits per side and n edges connecting pairs of exits, with no edges between exits on the same side and non-isomorphic under rotational symmetry. 4
 0, 2, 4, 22, 112, 1060, 11292, 149448, 2257288, 38720728, 740754220, 15648468804, 361711410384, 9081485302372, 246106843197984, 7160143986526240, 222595582448849152, 7364186944683168828, 258327454310582805036, 9577476294162996275928, 374205233351106756670120 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The case n=2 is a degenerate polygon (two sides connecting two vertices). The two possibilities are when the edges cross and do not cross. Polygons start at n=3 with a triangle. The sequence A132102 enumerates the case that edges are allowed between exits on the same side. This sequence can be enumerated in a similar manner using inclusion-exclusion on the number of sides that have their two exits connected. - Andrew Howroyd, Jan 26 2020 LINKS Andrew Howroyd, Table of n, a(n) for n = 1..200 Marko Riedel, Hexagonal tiles. Marko Riedel, Maple code for number of tiles using Burnside lemma. PROG (PARI) a(n) = {sumdiv(n, d, my(m=n/d); eulerphi(d)*sum(i=0, m, (-1)^i * binomial(m, i) * sum(j=0, m-i, (d%2==0 || m-i-j==0) * binomial(2*(m-i), 2*j) * d^j * (2*j)! / (j!*2^j) )))/n} \\ Andrew Howroyd, Jan 26 2020 CROSSREFS See A053871 for tiles with no rotational symmetries being taken into account, A289269 for tiles with rotational and reflectional symmetries being taken into account, A289343 for the same statistic evaluated when n is prime. Cf. A132102. Sequence in context: A080042 A324145 A165588 * A235938 A279705 A321248 Adjacent sequences:  A289188 A289189 A289190 * A289192 A289193 A289194 KEYWORD nonn AUTHOR Marko Riedel, Jun 27 2017 EXTENSIONS Terms a(14) and beyond from Andrew Howroyd, Jan 26 2020 STATUS approved

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Last modified September 21 10:03 EDT 2020. Contains 337268 sequences. (Running on oeis4.)