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A057812
Numbers k such that pi(k) is odd.
3
2, 5, 6, 11, 12, 17, 18, 23, 24, 25, 26, 27, 28, 31, 32, 33, 34, 35, 36, 41, 42, 47, 48, 49, 50, 51, 52, 59, 60, 67, 68, 69, 70, 73, 74, 75, 76, 77, 78, 83, 84, 85, 86, 87, 88, 97, 98, 99, 100, 103, 104, 105, 106, 109, 110, 111, 112, 127, 128, 129
OFFSET
1,1
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
Ping Ngai Chung and Shiyu Li, On the residue classes of π(n) modulo t, INTEGERS: Electronic Journal of Combinatorial Number Theory 13 (2013), A79.
FORMULA
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
MATHEMATICA
Position[Accumulate[Table[If[PrimeQ[n], 1, 0], {n, 150}]], _?OddQ]//Flatten (* Harvey P. Dale, Jan 30 2019 *)
PROG
(PARI) is(n)=primepi(n)%2 \\ Charles R Greathouse IV, Dec 19 2014
CROSSREFS
Sequence in context: A026344 A284488 A322047 * A329572 A329569 A140144
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Nov 07 2000
STATUS
approved