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A116568 Difference between n and the absolute value of the difference between number of nonprimes not exceeding n and number of primes not exceeding n. 1
0, 2, 2, 4, 4, 6, 6, 8, 8, 8, 10, 10, 12, 12, 12, 12, 14, 14, 16, 16, 16, 16, 18, 18, 18, 18, 18, 18, 20, 20, 22, 22, 22, 22, 22, 22, 24, 24, 24, 24, 26, 26, 28, 28, 28, 28, 30, 30, 30, 30, 30, 30, 32, 32, 32, 32, 32, 32, 34, 34, 36, 36, 36, 36, 36, 36, 38, 38, 38, 38, 40, 40, 42 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..5000

FORMULA

a(n) = n - Abs[A097454(n)].

EXAMPLE

a(11)=10 because the nonprimes not exceeding 11 are 1,4,6,8,9 and 10, the primes not exceeding 11 are 2,3,5,7 and 11 and 11-abs(6-5)=10.

MAPLE

with(numtheory): seq(n-abs(n-2*pi(n)), n=1..73);

MATHEMATICA

Table[n-Abs[2*PrimePi[n]-n], {n, 80}] (* Harvey P. Dale, Oct 08 2015 *)

PROG

(PARI) for(n=1, 50, print1(n - abs(2*primepi(n) - n) , ", ")) \\ G. C. Greubel, Sep 20 2017

CROSSREFS

Cf. A097454.

Sequence in context: A179291 A004079 A096494 * A239933 A061106 A319399

Adjacent sequences:  A116565 A116566 A116567 * A116569 A116570 A116571

KEYWORD

nonn

AUTHOR

Roger L. Bagula, Mar 18 2006

EXTENSIONS

Edited by N. J. A. Sloane, Apr 05 2006

STATUS

approved

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Last modified September 25 05:14 EDT 2021. Contains 347652 sequences. (Running on oeis4.)