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Search: id:A141771
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| A141771 |
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G.f.: (1-sqrt(1-4*x))/(2*x) + 8*x^3/((sqrt(1-4*x))*(1+sqrt(1-4*x))^3). |
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1
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| 1, 1, 2, 6, 19, 63, 216, 759, 2717, 9867, 36244, 134368, 501942, 1886966, 7131840, 27078705, 103221585, 394827315, 1514797020, 5827192140, 22469489130, 86825411010, 336145233840, 1303626531870, 5063559897474, 19695844095678, 76710709889576, 299125464317904
(list; graph; listen)
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OFFSET
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0,3
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REFERENCES
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M. Bona, Permutations with one or two 132-subsequences, Discrete Math., 181, 1998, 267-274.
R. Brignall et al., Decomposing simple permutations with enumerative consequences, Combinatorica, 28 (2008), 385-400.
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LINKS
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Miklos Bona, Permutations with one or two 132-subsequences, Discrete Math., 181 (1998) 267-274. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 18 2008]
R. Brignall, S. Huczynska, V. Vatter, Decomposing simple permutations with enumerative consequences, Combinatorica, 28 (2008) 384-400. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 18 2008]
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FORMULA
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a(n)=A000108(n)+A002054(n-2). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 18 2008]
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CROSSREFS
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Sequence in context: A109262 A006724 A057409 this_sequence A001170 A001168 A119255
Adjacent sequences: A141768 A141769 A141770 this_sequence A141772 A141773 A141774
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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), Sep 18 2008
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