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%I #10 Sep 21 2017 05:53:55
%S 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,
%T 18,18,20,20,22,22,22,22,22,22,24,24,24,24,26,26,28,28,28,28,30,30,30,
%U 30,30,30,32,32,32,32,32,32,34,34,36,36,36,36,36,36,38,38,38,38,40,40,42
%N Difference between n and the absolute value of the difference between number of nonprimes not exceeding n and number of primes not exceeding n.
%H G. C. Greubel, <a href="/A116568/b116568.txt">Table of n, a(n) for n = 1..5000</a>
%F a(n) = n - Abs[A097454(n)].
%e 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.
%p with(numtheory): seq(n-abs(n-2*pi(n)),n=1..73);
%t Table[n-Abs[2*PrimePi[n]-n],{n,80}] (* _Harvey P. Dale_, Oct 08 2015 *)
%o (PARI) for(n=1,50, print1(n - abs(2*primepi(n) - n) , ", ")) \\ _G. C. Greubel_, Sep 20 2017
%Y Cf. A097454.
%K nonn
%O 1,2
%A _Roger L. Bagula_, Mar 18 2006
%E Edited by _N. J. A. Sloane_, Apr 05 2006