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A153881 1 followed by -1, -1, -1, ... . 27
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 A002033.

LINKS

Table of n, a(n) for n=1..70.

Index entries for linear recurrences with constant coefficients, signature (1).

FORMULA

a(n) = 2*{C[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)

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: A121238 A131554 * A160357 A057077 A070748 A154990

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 December 18 20:06 EST 2018. Contains 318245 sequences. (Running on oeis4.)