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A202364
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Number of n-permutations with at least one cycle of length >=4.
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2
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0, 0, 0, 0, 6, 54, 444, 3828, 34404, 331812, 3457224, 38902104, 472682088, 6185876904, 86896701072, 1305666612144, 20907918062064, 355572850545648, 6401460197543904, 121637573726005152, 2432837939316094944, 51090380436082401504, 1123995659389121919168
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OFFSET
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0,5
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COMMENTS
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REFERENCES
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R. Sedgewick and P. Flajolet, Analysis of Algorithms, Addison Wesley, 1996, page 358.
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LINKS
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FORMULA
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E.g.f.: 1/(1-x) - exp(x + x^2/2 + x^3/3).
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MAPLE
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b:= proc(n) option remember; `if`(n<4, [6, 54, 444, 3828][n+1],
((5*n+3+n^2)*b(n-1) -(n+3)*b(n-2) -(n+3)*(n+2)*b(n-3)
-(n+3)*(n+2)*(n+1)^2*b(n-4))/n)
end:
a:= n-> `if`(n<4, 0, b(n-4)):
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MATHEMATICA
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nn=25; Range[0, nn]!CoefficientList[Series[1/(1-x)-Exp[x+x^2/2+x^3/3], {x, 0, nn}], x]
(* Second program: *)
b[n_] := b[n] = If[n<4, {6, 54, 444, 3828}[[n+1]], ((5*n+3+n^2)*b[n-1] - (n + 3)*b[n-2] - (n+3)*(n+2)*b[n-3] - (n+3)*(n+2)*(n+1)^2*b[n-4])/n]; a[n_] := If[n<4, 0, b[n-4]]; Table[a[n], {n, 0, 30}] (* Jean-François Alcover, Feb 08 2017, after Alois P. Heinz *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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