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Search: id:A092492
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| A092492 |
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Arises in enumeration of 321-hexagon-avoiding permutations. |
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+0
6
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| 0, 0, 0, 0, 0, 1, 5, 19, 68, 240, 839, 2911, 10054, 34641, 119203, 409893, 1408873, 4841373, 16634350, 57149111, 196333312, 674477710, 2317047808, 7959739375, 27343914410, 93933688630, 322686958885, 1108513737048, 3808031504891
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OFFSET
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1,7
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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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FORMULA
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a(n):=2*A058094(n-3)-5*A058094(n-4)+A058094(n-5) for n>=6. - Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 08 2004
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MAPLE
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b[1]:=1: b[2]:=2: b[3]:=5: b[4]:=14: b[5]:=42: b[6]:=132: for n from 6 to 45 do b[n+1]:=6*b[n]-11*b[n-1]+9*b[n-2]-4*b[n-3]-4*b[n-4]+b[n-5] od: a[1]:=0: a[2]:=0: a[3]:=0: a[4]:=0: a[5]:=0: for n from 6 to 40 do a[n]:=2*b[n-3]-5*b[n-4]+b[n-5] od: seq(a[n], n=1..40); (Deutsch)
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CROSSREFS
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Cf. A058094, A092489-A092491.
Sequence in context: A114277 A104496 A001435 this_sequence A070857 A047145 A055991
Adjacent sequences: A092489 A092490 A092491 this_sequence A092493 A092494 A092495
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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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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 08 2004
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