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Search: id:A110886
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| A110886 |
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Number of signed weighted Euler trees with total weight n (associated to even switching classes of matrices of order 2n). |
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+0
1
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| 1, 1, 3, 8, 27, 104, 436, 1930, 8871, 41916, 202300, 992942, 4940912, 24867870, 126371426, 647494746, 3341341155, 17350565376, 90593056624, 475333630402, 2504959102224, 13252904123786, 70366654738470, 374824160997086
(list; graph; listen)
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OFFSET
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0,3
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REFERENCES
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R. Bacher and D. Garber, Spindle-configurations of skew lines, submitted
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FORMULA
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sum _{n=0} ^\infty a_n z^n = {3(1-z)-\sqrt{(1-z)(1-5z-4z^2)} \over 2(1-z) }
a(n)=2+sum(k=1,n-1,a(n-k)*a(k)) - Benoit Cloitre (benoit7848c(AT)orange.fr), Jul 27 2008
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MAPLE
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G:=(3*(1-z)-sqrt((1-z)*(1-5*z-4*z^2)))/2/(1-z): Gser:=series(G, z=0, 32): seq(coeff(Gser, z, n), n=0..27); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Dec 31 2006
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CROSSREFS
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Sequence in context: A145760 A102318 A102206 this_sequence A104854 A030495 A074271
Adjacent sequences: A110883 A110884 A110885 this_sequence A110887 A110888 A110889
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KEYWORD
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nonn
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AUTHOR
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David Garber (garber(AT)hait.ac.il), Sep 19 2005
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Dec 31 2006
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