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Search: id:A092493
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| A092493 |
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a(n)=4a(n-1)-4a(n-2)+3a(n-3)+a(n-4)-a(n-5). |
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+0
1
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| 1, 2, 5, 14, 42, 128, 389, 1179, 3572, 10825, 32810, 99446, 301412, 913547, 2768863, 8392136, 25435699, 77092976, 233660832, 708201794, 2146486339, 6505777953, 19718339694, 59764246943, 181139247400, 549014312524, 1664005563066
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Arises in enumeration of certain pattern-avoiding permutations.
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REFERENCES
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Z. Stankova and J. West, Explicit enumeration of 321, hexagon-avoiding permutations, Discrete Math., 280 (2004), 165-189.
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MAPLE
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a[1]:=1: a[2]:=2: a[3]:=5: a[4]:=14: a[5]:=42: for n from 6 to 32 do a[n]:=4*a[n-1]-4*a[n-2]+3*a[n-3]+a[n-4]-a[n-5] od: seq(a[j], j=1..32); (Deutsch)
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CROSSREFS
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Cf. A058094, A092489-A092492.
Adjacent sequences: A092490 A092491 A092492 this_sequence A092494 A092495 A092496
Sequence in context: A000660 A025274 A132833 this_sequence A080937 A054392 A006930
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KEYWORD
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nonn,easy
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AUTHOR
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njas, Apr 04 2004
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EXTENSIONS
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Edited by Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 12 2005
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