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 A065357 a(n) = (-1)^pi(n) where pi(n) is the number of primes <= n. 3
 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 0,1 LINKS N. J. A. Sloane, Table of n, a(n) for n = 0..10000 (First 1000 terms from Harry J. Smith) MATHEMATICA (-1)^PrimePi[Range[0, 110]] (* Harvey P. Dale, Nov 02 2015 *) PROG (PARI) { for (n=0, 1000, if (n, a=(-1)^primepi(n), a=1); write("b065357.txt", n, " ", a) ) } \\ Harry J. Smith, Sep 30 2009 CROSSREFS Cf. A000720, A065358. Sequence in context: A130151 A143431 A064179 * A119665 A121241 A122188 Adjacent sequences: A065354 A065355 A065356 * A065358 A065359 A065360 KEYWORD easy,sign AUTHOR Jason Earls, Oct 31 2001 STATUS approved

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Last modified December 11 06:25 EST 2023. Contains 367717 sequences. (Running on oeis4.)