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A056449
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3^floor((n+1)/2).
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7
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3, 3, 9, 9, 27, 27, 81, 81, 243, 243, 729, 729, 2187, 2187, 6561, 6561, 19683, 19683, 59049, 59049, 177147, 177147, 531441, 531441, 1594323, 1594323, 4782969, 4782969, 14348907, 14348907, 43046721, 43046721, 129140163, 129140163
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Powers of 3 with positive exponent, repeated. [From Omar E. Pol, Jul 27 2009]
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REFERENCES
| M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia.
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 1..2000
Index to sequences with linear recurrences with constant coefficients, signature (0,3).
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FORMULA
| G.f. 3*x*(1+x) / ( 1-3*x^2 ). - R. J. Mathar, Jul 06 2011
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PROG
| (MAGMA) [3^Floor((n+1)/2): n in [1..40]]; // Vincenzo Librandi, Aug 16 2011
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CROSSREFS
| Cf. A000244, A016116.
Essentially the same as A108411.
Sequence in context: A145957 A128019 A108411 * A162436 A146788 A147244
Adjacent sequences: A056446 A056447 A056448 * A056450 A056451 A056452
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KEYWORD
| nonn,easy
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AUTHOR
| Marks R. Nester (nesterm(AT)dpi.qld.gov.au)
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EXTENSIONS
| Edited by N. J. A. Sloane, Jul 03 2009 at the suggestion of Klaus Brockhaus.
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