A321018 a(n) = round(pi(n)/2).

0, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13

Offset

1,5

Comments

More terms than usual are displayed in order to distinguish this from neighboring sequences.

Links

Table of n, a(n) for n=1..100.

Mathematica

Floor[#/2+1/2]&/@Accumulate[Table[If[PrimeQ[n], 1, 0], {n, 100}]] (* Harvey P. Dale, Feb 21 2022 *)

Crossrefs

Cf. A000720, A321017.

Suggested by A321005.

Sequence in context: A321017 A138194 A133876 * A340764 A152467 A242602

Adjacent sequences: A321015 A321016 A321017 * A321019 A321020 A321021

Keyword

nonn

Author

N. J. A. Sloane, Nov 09 2018

Status

approved