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A001473
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Number of degree-n permutations of order exactly 4.
(Formerly M4206 N1756)
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25
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0, 0, 0, 6, 30, 180, 840, 5460, 30996, 209160, 1290960, 9753480, 69618120, 571627056, 4443697440, 40027718640, 346953934320, 3369416698080, 31421601510336, 328430320909920, 3331475969159520, 37124416523261760
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OFFSET
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1,4
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REFERENCES
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N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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FORMULA
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E.g.f.: exp(x + x^2/2 + x^4/4) - exp(x + x^2/2).
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MATHEMATICA
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Rest@With[{m = 30}, CoefficientList[Series[Exp[x +x^2/2 +x^4/4] - Exp[x +x^2/2], {x, 0, m}], x]*Range[0, m]!] (* G. C. Greubel, May 14 2019 *)
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PROG
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(PARI) my(x=xx+O(xx^33)); concat([0, 0, 0], Vec(serlaplace(-exp(x+1/2*x^2) +exp(x+1/2*x^2+1/4*x^4)))) \\ Michel Marcus, Dec 12 2014
(Magma) m:=30; R<x>:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!( Exp(x + x^2/2 +x^4/4) -Exp(x+x^2/2) )); [0, 0, 0] cat [Factorial(n+3)*b[n]: n in [1..m-4]]; // G. C. Greubel, May 14 2019
(Sage) m = 30; T = taylor(exp(x +x^2/2 +x^4/4) - exp(x+x^2/2), x, 0, m); a=[factorial(n)*T.coefficient(x, n) for n in (0..m)]; a[1:] # G. C. Greubel, May 14 2019
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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