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Search: id:A094219
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| A094219 |
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Number of permutations of length n with exactly 3 occurrences of the pattern 2-13. |
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+0
7
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| 0, 0, 0, 0, 7, 112, 1092, 8400, 56100, 341088, 1939938, 10498488, 54679625, 276276000, 1362040680, 6580248480, 31256180280, 146350008000, 676868787000, 3097351569312, 14042319855102, 63144549413792, 281895309883000
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OFFSET
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1,5
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REFERENCES
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R. Lie, Permutations and Patterns, Master's Thesis, Goeteborg, Sweden: Chalmers University of Technology, 2004.
Robert Parviainen, Lattice Path Enumeration of Permutations with k Occurrences of the Pattern 2-13, Journal of Integer Sequences, Vol. 9 (2006), Article 06.3.2.
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FORMULA
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a(n)=(1/3)*binomial(n+2, 2)*binomial(2*n, n-5)
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PROGRAM
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(PARI) a(n)=1/3*binomial(n+2, 2)*binomial(2*n, n-5)
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CROSSREFS
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Cf. A094218.
Sequence in context: A009471 A061233 A117795 this_sequence A067404 A129030 A128576
Adjacent sequences: A094216 A094217 A094218 this_sequence A094220 A094221 A094222
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KEYWORD
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nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), May 27 2004
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