A177691 The odd values of PrimePi(.), with repetition.

1, 3, 3, 5, 5, 7, 7, 9, 9, 9, 9, 9, 9, 11, 11, 11, 11, 11, 11, 13, 13, 15, 15, 15, 15, 15, 15, 17, 17, 19, 19, 19, 19, 21, 21, 21, 21, 21, 21, 23, 23, 23, 23, 23, 23, 25, 25, 25, 25, 27, 27, 27, 27, 29, 29, 29, 29, 31, 31, 31, 31, 33, 33, 35, 35, 37, 37, 37, 37, 37, 37, 39, 39, 39

Offset

1,2

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Formula

Obtained by removing all even numbers from A000720. Block lengths (frequencies of repetitions) are in A078584.

Maple

seq((2*n-1)$(ithprime(2*n)-ithprime(2*n-1)), n=1..30); # Robert Israel, Feb 13 2019

Mathematica

Select[PrimePi[Range[300]], OddQ] (* Harvey P. Dale, Dec 24 2014 *)

Crossrefs

Cf. A000720, A005408.

Sequence in context: A088524 A129337 A133909 * A206913 A117767 A340836

Adjacent sequences: A177688 A177689 A177690 * A177692 A177693 A177694

Keyword

nonn,easy

Author

Giovanni Teofilatto, May 11 2010

Extensions

Erroneous formula removed by R. J. Mathar, May 14 2010

Status

approved