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Search: id:A111283
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| A111283 |
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Number of permutations avoiding the patterns {4321,45132,45231,35412,53412,45213,43512,45312,456123,451623,356124}; number of strong sorting class based on 4321. |
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1
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| 1, 2, 6, 23, 96, 409, 1751, 7505, 32176, 137956, 591501, 2536132, 10873981, 46623553, 199904321, 857114814, 3674987126, 15756967635, 67559972476, 289671844661, 1242004318751, 5325249092137, 22832672531956, 97897943538708
(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)+a(n-2)+a(n-3)-4; n>=4.
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MATHEMATICA
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a[1] = 1; a[2] = 2; a[3] = 6; a[n_] := a[n] = 4a[n - 1] + a[n - 2] + a[n - 3] - 4; Table[a[n], {n, 24}] (* Robert G. Wilson v *)
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CROSSREFS
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Adjacent sequences: A111280 A111281 A111282 this_sequence A111284 A111285 A111286
Sequence in context: A110068 A012866 A134064 this_sequence A009449 A133656 A078487
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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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