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 A153881 1 followed by -1, -1, -1, ... . 28
 1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Dirichlet inverse of A074206. LINKS Index entries for linear recurrences with constant coefficients, signature (1). FORMULA a(n) = 2*(binomial(2*(n-1), n-1) mod 2) - 1, with n >= 1. - Paolo P. Lava, Jan 22 2009 G.f: x*(1-2*x)/(1-x). - Mats Granvik, Mar 09 2009, rewritten R. J. Mathar, Mar 31 2010 a(n) = (-1)^A000040(n). - Juri-Stepan Gerasimov, Sep 10 2009 G.f.: x / (1 + x / (1 - 2*x)). - Michael Somos, Apr 02 2012 From Wesley Ivan Hurt, Jun 20 2014: (Start) a(1) = 1; a(n) = -1, n > 1. a(n) = 1 - 2*sign(n-1) = 1 - 2*A057427(n-1). a(n) = (-1)^sign(1-n) = (-1)^A057427(1-n). a(n) = 2*floor(1/n)-1 = 2*A063524(n)-1. (End) Dirichlet g.f.: 2 - zeta(s). - Álvar Ibeas, Dec 30 2018 MAPLE A153881:=n->`if`(n=1, 1, -1); seq(A153881(n), n=1..100); # Wesley Ivan Hurt, Jun 20 2014 MATHEMATICA Table[1 - 2 Sign[n - 1], {n, 100}] (* Wesley Ivan Hurt, Jun 20 2014 *) PROG (MAGMA) [1 - 2*Sign(n-1) : n in [1..100]]; // Wesley Ivan Hurt, Jun 20 2014 (PARI) a(n)=if(n>1, -1, 1) \\ Charles R Greathouse IV, Sep 24 2015 CROSSREFS If prefixed by initial 0, we get A134824. Sequence in context: A186032 A212157 A131554 * A160357 A186039 A057077 Adjacent sequences:  A153878 A153879 A153880 * A153882 A153883 A153884 KEYWORD sign,easy AUTHOR Mats Granvik, Jan 03 2009 EXTENSIONS Edited by Charles R Greathouse IV, Mar 18 2010 STATUS approved

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Last modified January 21 05:39 EST 2020. Contains 331104 sequences. (Running on oeis4.)