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Search: id:A000517
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| A000517 |
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Number of permutations of length n with exactly three valleys.
(Formerly M5431 N2360)
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+0
7
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| 272, 7936, 137216, 1841152, 21253376, 222398464, 2174832640, 20261765120, 182172651520, 1594922762240, 13684856848384, 115620218667008, 965271355195392, 7984436548730880
(list; graph; listen)
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OFFSET
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7,1
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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).
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
F. N. David, M. G. Kendall and D. E. Barton, Symmetric Function and Allied Tables, Cambridge, 1966, p. 261.
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LINKS
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R. G. Rieper and M. Zeleke, Valleyless Sequences
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FORMULA
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G.f. 16x^7(17-184x+636x^2-720x^3)/((1-2x)^4*(1-4x)^3*(1-6x)^2*(1-8x)). - Ralf Stephan (ralf(AT)ark.in-berlin.de), Sep 18 2003
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CROSSREFS
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Cf. A000431, A000487.
Sequence in context: A133514 A158587 A141546 this_sequence A023907 A035842 A000518
Adjacent sequences: A000514 A000515 A000516 this_sequence A000518 A000519 A000520
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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).
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EXTENSIONS
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More terms from Ralf Stephan (ralf(AT)ark.in-berlin.de), Sep 18 2003
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