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A011957
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Number of ZnS polytypes that repeat after n layers.
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0
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0, 1, 1, 1, 1, 2, 3, 6, 10, 18, 31, 59, 105, 198, 365, 688, 1285, 2438, 4599, 8755, 16647, 31806, 60787, 116570, 223696, 430290, 828514, 1598025, 3085465, 5965612, 11545611, 22370304, 43383539, 84216330, 163617801, 318148208
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,6
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COMMENTS
| Also the number of orbits of the symmetric group S3 action on irreducible polynomials of degree n>1 over GF(2). [From Jean-Francis Michon, Philippe Ravache (philippe.ravache(AT)univ-rouen.fr), Oct 04 2009]
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REFERENCES
| T. J. McLarnan, The numbers of polytypes ..., Zeits. Krist. 155, 269-291 (1981).
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FORMULA
| a(n) = 1 if n=2, A000048(n) + A165920(n) + A165921(n) if n>2. [From Jean-Francis Michon, Philippe Ravache (philippe.ravache(AT)univ-rouen.fr), Oct 04 2009]
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CROSSREFS
| A000048 is the number of 3-elements orbits, A165920 is the number of 2-elements orbits and A165921 is the number of 6-elements orbits. [From Jean-Francis Michon, Philippe Ravache (philippe.ravache(AT)univ-rouen.fr), Oct 04 2009]
Sequence in context: A023359 A082482 A066000 * A019436 A147852 A061279
Adjacent sequences: A011954 A011955 A011956 * A011958 A011959 A011960
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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