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A282029 a(n) = n - pi(n/2). 3

%I

%S 0,1,2,3,3,4,4,5,6,7,7,8,9,10,10,11,12,13,14,15,16,17,17,18,19,20,20,

%T 21,22,23,24,25,26,27,27,28,29,30,30,31,32,33,34,35,36,37,37,38,39,40,

%U 41,42,43,44,45,46,47,48,48,49,50,51,51,52,53,54,55,56,57,58,59,60,61,62,62,63,64,65,66,67,68

%N a(n) = n - pi(n/2).

%H Vincenzo Librandi, <a href="/A282029/b282029.txt">Table of n, a(n) for n = 0..10000</a>

%t Table[n - PrimePi[n/2], {n, 0, 100}] (* _Vincenzo Librandi_, Feb 18 2017 *)

%o (MAGMA) [0,1] cat [ n-#PrimesUpTo(n div 2): n in [2..90] ]; // _Vincenzo Librandi_, Feb 18 2017

%o (PARI) a(n)=n - primepi(n\2) \\ _Charles R Greathouse IV_, Feb 18 2017

%Y Cf. A000720, A282028.

%K nonn

%O 0,3

%A _N. J. A. Sloane_, Feb 17 2017

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Last modified September 26 09:15 EDT 2021. Contains 347664 sequences. (Running on oeis4.)