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Search: id:A007056
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| A007056 |
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Number of words of length n in a certain language.
(Formerly M2781)
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+0
1
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| 1, 3, 9, 21, 57, 123, 279, 549, 1209, 2127, 4689
(list; graph; listen)
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OFFSET
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0,2
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
R. Kemp, On the number of words in the language {w in Sigma* | w = w^R }^2, Discrete Math., 40 (1982), 225-234.
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CROSSREFS
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Sequence in context: A111209 A109755 A005254 this_sequence A026551 A060578 A147078
Adjacent sequences: A007053 A007054 A007055 this_sequence A007057 A007058 A007059
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Mira Bernstein, R. Kemp
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