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A046718
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Number of permutations of [ n ] with exactly 1 132-pattern and 2 123-patterns.
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0
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1, 4, 14, 47, 152, 472, 1408, 11264, 30464, 80384, 207616, 526336, 1312768, 3227648, 7835648, 18808832, 44695552, 105250816, 245825536, 569901056, 1312292864, 3003121664, 6833569792
(list; graph; refs; listen; history; internal format)
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OFFSET
| 4,2
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REFERENCES
| The Number of Permutations With a Prescribed Number of 132 and 123 Patterns, S.Ekhad, A.Robertson, D.Zeilberger, preprint
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LINKS
| link to preprint
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FORMULA
| G.f.: -x^4*(x^3-6*x^2+4*x-1)/(1-2*x)^2
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EXAMPLE
| a(5)=4: [ 12345 ]->[ 24351 ], [ 24315 ], [ 51324 ], or [ 41325 ]
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CROSSREFS
| Cf. A001815, A001787, A011782, A001793.
Sequence in context: A124805 A121530 A121299 * A192877 A104487 A094789
Adjacent sequences: A046715 A046716 A046717 * A046719 A046720 A046721
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KEYWORD
| nonn
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AUTHOR
| Len Smiley (smiley(AT)math.uaa.alaska.edu)
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