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A006873
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Number of alternating 4-signed permutations.
(Formerly M4430)
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5
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1, 1, 7, 47, 497, 6241, 95767, 1704527, 34741217, 796079041, 20273087527, 567864586607, 17352768515537, 574448847467041, 20479521468959287, 782259922208550287, 31872138933891307457, 1379749466246228538241, 63243057486503656319047, 3059895336952604166395567
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OFFSET
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0,3
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REFERENCES
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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.: (sin(x) + cos(3*x)) / cos(4*x). - M. F. Hasler, Apr 28 2013
a(n) = Re(2*((1-I)/(1+I))^n*(1 + Sum_{j=0..n}(binomial(n,j)*Li_{-j}(I)* 4^j))). - Peter Luschny, Apr 29 2013
a(n) ~ sqrt(2-sqrt(2)) * 2^(3*n+3/2) * n^(n+1/2) / (Pi^(n+1/2) * exp(n)). - Vaclav Kotesovec, Feb 25 2014
a(n) ~ GAMMA(n)*8^n/(Pi^n*(2*sqrt(4+2*sqrt(2)))). - Simon Plouffe, Nov 29 2018
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MAPLE
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per4 := proc(n) local j; 2*((1-I)/(1+I))^n*(1+add(binomial(n, j)* polylog(-j, I)*4^j, j=0..n)) end: A006873 := n -> Re(per4(n));
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MATHEMATICA
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mx = 17; Range[0, mx]! CoefficientList[ Series[ (Sin[x] + Cos[3x])/Cos[4x], {x, 0, mx}], x] (* Robert G. Wilson v, Apr 28 2013 *)
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PROG
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(PARI) x='x+O('x^66); Vec(serlaplace((sin(x)+cos(3*x))/cos(4*x))) \\ Joerg Arndt, Apr 28 2013
(Magma) m:=50; R<x>:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!(Sin(x)+Cos(3*x))/Cos(4*x))); [Factorial(n-1)*b[n]: n in [1..m-1]]; // G. C. Greubel, Nov 29 2018
(Sage)
f=(sin(x) + cos(3*x))/cos(4*x)
g=f.taylor(x, 0, 50)
L=g.coefficients()
coeffs={c[1]:c[0]*factorial(c[1]) for c in L}
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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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