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Search: id:A054873
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| A054873 |
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Number of (S_5 67)-avoiding permutations. |
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+0
2
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| 1, 2, 6, 24, 120, 720, 5040, 40320, 357840, 3427200, 34685280, 365541120, 3971615760, 44181889920, 500788985760, 5763231048960, 67163932069920, 791030794095360, 9400660122813120, 112587818898562560
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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E. Barcucci, A. Del Lungo, E. Pergola, R. Pinzani, Permutations avoiding an increasing number of length-increasing forbidden subsequences, Discrete MAthematics and Theoretical Computer Science 4, 2000, 31-44
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LINKS
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E. Barcucci, A. Del Lungo, E. Pergola and R. Pinzani, Permutations avoiding an increasing number of length-increasing forbidden subsequences
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FORMULA
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f := (x, j)->1-(j+1)*x- sqrt(1-2*(j+1)*x+(j-1)^2*x^2); t := (x, j)->sum(k!*x^k, k=1..(j-1)); s := (x, j)->x^(j-2)*(j-1)!*(f(x, j))/(2)+ t(x, j); j := 6
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CROSSREFS
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Cf. A000108.
Sequence in context: A072131 A067455 A033646 this_sequence A072132 A066459 A071937
Adjacent sequences: A054870 A054871 A054872 this_sequence A054874 A054875 A054876
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KEYWORD
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nonn
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AUTHOR
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Elisa Pergola (elisa(AT)dsi.unifi.it), May 26 2000
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