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 A006535 Number of one-sided hexagonal polyominoes with n cells. (Formerly M2846) 12
 1, 1, 3, 10, 33, 147, 620, 2821, 12942, 60639, 286190, 1364621, 6545430, 31586358, 153143956, 745700845, 3644379397, 17869651166, 87877879487, 433301253231, 2141584454057, 10607707971062, 52646117638427, 261756764824964, 1303625908234997, 6502430891223011, 32480041218465452, 162454295068924189, 813541940383789255, 4078750395194965720 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 REFERENCES J. Meeus, personal communication. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS John Mason, Table of n, a(n) for n = 1..36 J. Meeus & N. J. A. Sloane, Correspondence, 1974-1975 Ed Pegg, Jr., Illustrations of polyforms Eric Weisstein's World of Mathematics, Polyhex FORMULA a(n) = 2*A000228(n) - A030225(n). CROSSREFS Cf. A000228, A030225, A001207. Sequence in context: A326558 A149031 A145928 * A041633 A308499 A034215 Adjacent sequences: A006532 A006533 A006534 * A006536 A006537 A006538 KEYWORD nonn,hard,nice AUTHOR N. J. A. Sloane EXTENSIONS a(7)-a(12) from David W. Wilson a(13) from Achim Flammenkamp, Feb 15 1999 a(14)-a(20) from Joseph Myers, Sep 21 2002 a(21)-a(30) from John Mason, Jul 18 2023 STATUS approved

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Last modified May 19 03:29 EDT 2024. Contains 372666 sequences. (Running on oeis4.)