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 A006873 Number of alternating 4-signed permutations. (Formerly M4430) 5
 1, 1, 7, 47, 497, 6241, 95767, 1704527, 34741217, 796079041, 20273087527, 567864586607, 17352768515537, 574448847467041, 20479521468959287, 782259922208550287, 31872138933891307457, 1379749466246228538241, 63243057486503656319047, 3059895336952604166395567 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..200 R. Ehrenborg and M. A. Readdy, Sheffer posets and r-signed permutations, Preprint, 1994. (Annotated scanned copy) Richard Ehrenborg and Margaret A. Readdy, Sheffer posets and r-signed permutations, Annales des Sciences Mathématiques du Québec, 19 (1995), 173-196. FORMULA 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*(sqrt(4+2*sqrt(2)))). - Simon Plouffe, Nov 29 2018 MAPLE 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)); seq(A006873(i), i=0..11); # Peter Luschny, Apr 29 2013 MATHEMATICA mx = 17; Range[0, mx]! CoefficientList[ Series[ (Sin[x] + Cos[3x])/Cos[4x], {x, 0, mx}], x] (* Robert G. Wilson v, Apr 28 2013 *) PROG (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:=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} coeffs # G. C. Greubel, Nov 29 2018 CROSSREFS Cf. A007286, A007289, A225109. Sequence in context: A173772 A178002 A288722 * A228695 A268063 A015097 Adjacent sequences:  A006870 A006871 A006872 * A006874 A006875 A006876 KEYWORD nonn,changed AUTHOR EXTENSIONS Added more terms, Joerg Arndt, Apr 28 2013 STATUS approved

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Last modified December 10 14:50 EST 2018. Contains 318049 sequences. (Running on oeis4.)