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%I #11 Nov 14 2012 12:57:48
%S 0,1,1,0,0,1,1,1,0,1,1,0,1,1,0,0,1,1,1,1,1,1,0,1,1,0,1,1,0,0,1,0,1,1,
%T 1,1,1,1,1
%N Parity of pi(5^n).
%C The parity of pi(n) is obtained without calculating pi(n), and much more quickly. See the paper below.
%H Henri Lifchitz, <a href="http://www.primenumbers.net/Henri/us/ParPius.htm">Parity of pi(n)</a>
%e a(4) = pi(5^4) mod 2 = 114 mod 2 = 0.
%t Table[Mod[PrimePi[5^n], 2], {n, 10}]
%Y Cf. A006880, A219071, A219097, A219098.
%K nonn
%O 0
%A _Henri Lifchitz_, Nov 14 2012
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