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1, 21, 441, 9261, 194481, 4084101, 85766121, 1801088541, 37822859361, 794280046581, 16679880978201, 350277500542221, 7355827511386641, 154472377739119461, 3243919932521508681, 68122318582951682301, 1430568690241985328321, 30041942495081691894741, 630880792396715529789561, 13248496640331026125580781, 278218429446951548637196401
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| The compositions of n in which each natural number is colored by one of p different colors are called p-colored compositions of n. For n>=1, a(n) equals the number of 21-colored compositions of n such that no adjacent parts have the same color. - Milan Janjic, Nov 17 2011
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LINKS
| T. D. Noe, Table of n, a(n) for n = 0..100
Tanya Khovanova, Recursive Sequences
Index to sequences with linear recurrences with constant coefficients, signature (21).
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FORMULA
| For A009966-A009992 we have g.f.: 1/(1-qx), e.g.f.: exp(qx), with q = 21, 22, ..., 48. - Dan Fux (dan.fux(AT)OpenGaia.com or danfux(AT)OpenGaia.com), Apr 07 2001
a(n)=21^n; a(n)=21*a(n-1) n>0 a(0)=1 [From Vincenzo Librandi, Nov 21 2010]
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PROG
| (Other) sage: [lucas_number1(n, 21, 0) for n in xrange(1, 17)]# [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Apr 29 2009]
(MAGMA)[21^n: n in [0..100]][From Vincenzo Librandi, Nov 21 2010]
(PARI) a(n)=21^n \\ Charles R Greathouse IV, Nov 18 2011
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CROSSREFS
| Sequence in context: A189060 A167255 A171295 * A189433 A041842 A199252
Adjacent sequences: A009962 A009963 A009964 * A009966 A009967 A009968
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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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