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%I #10 Jun 23 2024 22:02:57
%S 2,5,6,11,12,17,18,23,24,25,26,27,28,31,32,33,34,35,36,41,42,47,48,49,
%T 50,51,52,59,60,67,68,69,70,73,74,75,76,77,78,83,84,85,86,87,88,97,98,
%U 99,100,103,104,105,106,109,110,111,112,127,128,129
%N Numbers k such that pi(k) is odd.
%H Charles R Greathouse IV, <a href="/A057812/b057812.txt">Table of n, a(n) for n = 1..10000</a>
%H Ping Ngai Chung and Shiyu Li, <a href="http://www.emis.de/journals/INTEGERS/papers/n79/n79.Abstract.html"> On the residue classes of π(n) modulo t</a>, INTEGERS: Electronic Journal of Combinatorial Number Theory 13 (2013), A79.
%F Chang & Li show that a(n) < 64n + o(1), and a(n) < 8n + o(1) under the Hardy-Littlewood prime tuples conjecture. - _Charles R Greathouse IV_, Dec 19 2014
%t Position[Accumulate[Table[If[PrimeQ[n],1,0],{n,150}]],_?OddQ]//Flatten (* _Harvey P. Dale_, Jan 30 2019 *)
%o (PARI) is(n)=primepi(n)%2 \\ _Charles R Greathouse IV_, Dec 19 2014
%Y Cf. A000720, A057811.
%K nonn
%O 1,1
%A _N. J. A. Sloane_, Nov 07 2000
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