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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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0
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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; refs; listen; history; internal format)
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OFFSET
| 1,2
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REFERENCES
| 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
| a(n)=4a(n-1)+a(n-2)+a(n-3)-4; n>=4.
Empirical G.f.: x*(1-3*x-x^2-x^3)/(1-5*x+3*x^2+x^4). [Colin Barker, Jan 16 2012]
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MATHEMATICA
| 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
| Sequence in context: A150295 A150296 A134064 * A150297 A150298 A196018
Adjacent sequences: A111280 A111281 A111282 * A111284 A111285 A111286
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KEYWORD
| nonn
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AUTHOR
| Len Smiley ( smiley (at) math.uaa.alaska.edu ), Nov 01 2005
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EXTENSIONS
| More terms from Robert G. Wilson v (rgwv(at)rgwv.com), Nov 04 2005
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