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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
J. Meeus & N. J. A. Sloane, Correspondence, 1974-1975
Eric Weisstein's World of Mathematics, Polyhex
FORMULA
a(n) = 2*A000228(n) - A030225(n).
CROSSREFS
Sequence in context: A326558 A149031 A145928 * A041633 A308499 A034215
KEYWORD
nonn,hard,nice
AUTHOR
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.)