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 A261012 Sign(n) (with offset -1): a(n) = 1 if n>0, = -1 if n<0, = 0 if n = 0. 2
 -1, 0, 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, 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 For nonnegative n, partial sums of A063524 (characteristic function of 1). - Jeremy Gardiner, Sep 08 2002 For nonnegative n, characteristic function of positive integers. - Franklin T. Adams-Watters, Aug 01 2011 a(A000027(n)) = 1; a(A000004(n)) = 0. - Reinhard Zumkeller, Oct 11 2008 Central terms of the triangle in A152487. - Reinhard Zumkeller, Dec 06 2008 n-th prime mod 2 (with offset 1,1). - Philippe Deléham, Apr 04 2009 REFERENCES T. M. Macrobert, Functions of a Complex Variable, 4th ed., Macmillan and Co, London, 1958, p. 90 LINKS Index entries for linear recurrences with constant coefficients, signature (1). FORMULA G.f.: Sum_{k>=0} 2^k*x^(2^k)/(1+x^(2^k)). - Michael Somos, Sep 11 2005 For n>=0, a(n) = A000007(0^n). - Jaume Oliver Lafont, Mar 19 2009 a(0) = 0, a(n) = n/|n| or |n|/n for n != 0. - Jon Perry, Sep 20 2012 G.f.: -(x^2+x-1) / (x*(x-1)). - Colin Barker, Mar 13 2014 MAPLE with(numtheory); A057427:=n->signum(n); seq(A057427(k), k=-1..50); # Wesley Ivan Hurt, Oct 22 2013 MATHEMATICA Sign[Range[-1, 120]] (* or *) PadRight[{-1, 0}, 120, {1}] (* Harvey P. Dale, May 12 2019 *) PROG (PARI) a(n)=sign(n) (Haskell) a261012 = signum a261012_list = -1 : 0 : [1, 1 ..] -- Reinhard Zumkeller, Nov 28 2012 CROSSREFS A057427 is the official entry for sign(n) or signum(n). - N. J. A. Sloane, Aug 16 2015 Sequence in context: A105812 A134323 A060576 * A019590 A154955 A240356 Adjacent sequences:  A261009 A261010 A261011 * A261013 A261014 A261015 KEYWORD easy,sign,mult AUTHOR Henry Bottomley, Sep 05 2000 EXTENSIONS a(-1) = -1 added by Jon Perry, Sep 20 2012 Incorrect g.f. and e.g.f. removed by Joerg Arndt, Oct 22 2013 The initial a(-1)=-1 should never have been added. STATUS approved

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Last modified December 14 07:03 EST 2019. Contains 329978 sequences. (Running on oeis4.)