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Search: id:A006857
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| A006857 |
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Number of permutations of n+5 which avoid the pattern 132 and have exactly 4 descents. (Formerly M4977)
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+0 5
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| 1, 15, 105, 490, 1764, 5292, 13860, 32670, 70785, 143143, 273273, 496860, 866320, 1456560, 2372112, 3755844, 5799465, 8756055, 12954865, 18818646, 26883780, 37823500, 52474500, 71867250, 97260345, 130179231, 172459665, 226296280
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Kekule numbers for certain benzenoids. - Emeric Deutsch (deutsch(AT)duke.poly.edu), Nov 18 2005
Partial sums of A114242. - Peter Bala (pbala(AT)toucansurf.com), Sep 21 2007
Dimensions of certain Lie algebra (see reference for precise definition).
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REFERENCES
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S. J. Cyvin and I. Gutman, Kekule structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (pp. 167-169, Table 10.5/II/1).
G. Kreweras, Traitemant simultane du "Probleme de Young" et du "Probleme de Simon Newcomb", Cahiers du Bureau Universitaire de Recherche Op\'{e}rationnelle. Institut de Statistique, Universit\'{e} de Paris, 10 (1967), 23-31.
J. M. Landsberg and L. Manivel, The sextonions and E7 1/2, Adv. Math. 201 (2006), 143-179. [Th. 7.3, case a=4]
S. Mukai, An Introduction to Invariants and Moduli, Cambridge, 2003; see p. 239.
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FORMULA
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(4+n)!*(5+n)!/(2880*n!*(n+1)!). E.g.f.: 1/2880*(2880+40320*x+109440*x^2+105120*x^3+45000*x^4+9504*x^5+1016*x^6+52*x^7+x^8)*exp(x). - Vladeta Jovovic (vladeta(AT)Eunet.yu), Jan 29 2003
a(n) = C(n+4, 8)+6 C(n+5, 8)+6 C(n+6, 8)+C(n+7, 8) a(n) = C(n+3, 4)C(n+4, 4)/5 o.g.f. (1+6x+6x^2+x^3)/(1-x)^9 - Mike Zabrocki (zabrocki(AT)mathstat.yorku.ca), Aug 26 2004
a(n)=A001263(n+5,5)= binomial(n+5,5)*binomial(n+5,4)/(n+5), n>=0.
O.g.f.: (1+6*x+6*x^2+x^3)/(1-x)^9. Numerator polynomial is the fourth row polynomial of the Narayana triangle. W. Lang Nov 13 2007.
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MAPLE
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a:=n->(n+1)*(n+2)^2*(n+3)^2*(n+4)^2*(n+5)/2880: seq(a(n), n=0..38); (Deutsch)
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CROSSREFS
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Cf. A001263.
5th column of the table of Narayana numbers A001263
Cf. A114242.
Sequence in context: A010931 A076767 A022610 this_sequence A000478 A055848 A058085
Adjacent sequences: A006854 A006855 A006856 this_sequence A006858 A006859 A006860
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KEYWORD
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nonn
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AUTHOR
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Simon Plouffe (plouffe(AT)math.uqam.ca)
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EXTENSIONS
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More terms from Vladeta Jovovic (vladeta(AT)Eunet.yu), Jan 29 2003
Better description from Mike Zabrocki (zabrocki(AT)mathstat.yorku.ca), Aug 26 2004
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