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Search: id:A111280
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| A111280 |
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Number of permutations avoiding the patterns {4231,4321,35142,45312,42513,45132,35412,45213,43512,456123,351624,451623,356124}; number of strong sorting class based on 4231. |
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1
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| 1, 2, 6, 22, 113, 431, 1584, 5920, 22214, 83239, 311777, 1167902, 4375090, 16389450, 61395989, 229993639, 861572476, 3227511492, 12090486122, 45291815419, 169666341761, 635582108218, 2380935499534, 8919152662622, 33411776268873
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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M. Albert, R. Aldred, M. Atkinson, C Handley, D. Holton, D. McCaughan and H. van Ditmarsch, Sorting Classes, Elec. J. of Comb. 12 (2005)
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FORMULA
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a(n)=4a(n-1)-2a(n-2)+4a(n-3)-a(n-5)
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MATHEMATICA
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a[1] = 1; a[2] = 2; a[3] = 6; a[4] = 22; a[5] = 113; a[n_] := a[n] = 4a[n - 1] - 2a[n - 2] + 4a[n - 3] - a[n - 5]; Table[ a[n], {n, 25}] (* Robert G. Wilson v *)
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CROSSREFS
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Sequence in context: A064643 A129535 A014371 this_sequence A095817 A101042 A032266
Adjacent sequences: A111277 A111278 A111279 this_sequence A111281 A111282 A111283
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KEYWORD
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nonn
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AUTHOR
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Len Smiley ( smiley (at) math.uaa.alaska.edu ), Nov 01 2005
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(at)rgwv.com), Nov 04 2005
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