A057812 pi(n) is odd.

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

Cf. A000720, A057811.

Sequence in context: A026344 A284488 A322047 * A329572 A329569 A140144

Adjacent sequences: A057809 A057810 A057811 * A057813 A057814 A057815

Keyword

nonn

Author

N. J. A. Sloane, Nov 07 2000

Status

approved