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A007057
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Let S denote the palindromes in the language {0,1,2,3}*; a(n) = number of words of length n in the language SS.
(Formerly M3510)
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2
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1, 4, 16, 40, 136, 304, 880, 1768, 4936, 9112, 25216, 45016, 121600, 212944, 571552, 982240, 2616136, 4456384, 11785408, 19922872, 52402336, 88076560, 230641504, 385875880, 1006499200, 1677720304, 4361862976, 7247738776, 18789905872, 31138512784, 80529599680, 133143986056, 343594756936
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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REFERENCES
| R. Kemp, On the number of words in the language {w in Sigma* | w = w^R }^2, Discrete Math., 40 (1982), 225-234.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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MAPLE
| See A007055.
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CROSSREFS
| Sequence in context: A121318 A152133 A110477 * A056373 A018828 A114211
Adjacent sequences: A007054 A007055 A007056 * A007058 A007059 A007060
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Mira Bernstein, R. Kemp
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EXTENSIONS
| Entry revised by N. J. A. Sloane, Mar 07 2011
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