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 A046980 Numerators of Taylor series for exp(x)*cos(x). 4
 1, 1, 0, -1, -1, -1, 0, 1, 1, 1, 0, -1, -1, -1, 0, 1, 1, 1, 0, -1, -1, -1, 0, 1, 1, 1, 0, -1, -1, -1, 0, 1, 1, 1, 0, -1, -1, -1, 0, 1, 1, 1, 0, -1, -1, -1, 0, 1, 1, 1, 0, -1, -1, -1, 0, 1, 1, 1, 0, -1, -1, -1, 0, 1, 1, 1, 0, -1, -1, -1, 0, 1, 1, 1, 0, -1, -1, -1, 0, 1, 1, 1, 0, -1, -1, -1, 0, 1, 1, 1, 0, -1, -1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Lehmer sequence U_n for R=2 Q=1. [Artur Jasinski, Oct 06 2008] REFERENCES G. W. Caunt, Infinitesimal Calculus, Oxford Univ. Press, 1914, p. 477. LINKS Index entries for linear recurrences with constant coefficients, signature (0, 0, 0, -1). FORMULA G.f.: (1+x-x^3)/(1+x^4). a(n) = (b^(n+1) - c^(n+1))/(b - c) where b = sqrt(2)-((1 + I)/sqrt(2)), c = (1 + I)/sqrt(2). [Artur Jasinski, Oct 06 2008] EXAMPLE 1 + 1*x - (1/3)*x^3 - (1/6)*x^4 - (1/30)*x^5 + (1/630)*x^7 + (1/2520)*x^8 + (1/22680)*x^9 - ... MAPLE A046980 := n -> `if`(n mod 4 = 2, 0, (-1)^floor((n+1)/4)): seq(A046980(n), n=0..92); # Peter Luschny, Jun 16 2017 MATHEMATICA b = -((1 + I)/Sqrt[2]) + Sqrt[2]; c = (1 + I)/Sqrt[2]; Table[ Round[(b^n - c^n)/(b - c)], {n, 2, 200}] (* Artur Jasinski, Oct 06 2008 *) LinearRecurrence[{0, 0, 0, -1}, {1, 1, 0, -1}, 100] (* Jean-François Alcover, Apr 01 2016 *) CROSSREFS Cf. A046981. Sequence in context: A229343 A085369 A188082 * A152822 A118831 A118828 Adjacent sequences: A046977 A046978 A046979 * A046981 A046982 A046983 KEYWORD sign,frac,easy,nice AUTHOR STATUS approved

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Last modified December 5 15:27 EST 2022. Contains 358588 sequences. (Running on oeis4.)