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A219097 Parity of pi(2^n). 4
0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET
0
COMMENTS
The parity of pi(n) can be obtained without calculating pi(n), and much more quickly. See the paper below.
LINKS
Henri Lifchitz, Parity of pi(n)
FORMULA
a(n) = A000035(A007053(n)). - David Baugh, Nov 06 2020
EXAMPLE
For n = 5 , pi(2^5) = 11 = 1 (mod 2) = 1.
MAPLE
A071986 := proc(n)
numtheory[pi](n) mod 2 ;
end proc:
A219097 := proc(n)
A071986(2^n) ;
end proc: # R. J. Mathar, Nov 12 2012
MATHEMATICA
Table[Mod[PrimePi[2^n], 2], {n, 32}] (* Alonso del Arte, Nov 12 2012 *)
CROSSREFS
Sequence in context: A189664 A260446 A096268 * A284751 A288426 A286052
KEYWORD
nonn
AUTHOR
Henri Lifchitz, Nov 11 2012
EXTENSIONS
a(91) from David Baugh, Nov 06 2020
STATUS
approved

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Last modified March 19 01:57 EDT 2024. Contains 370952 sequences. (Running on oeis4.)