A321018 - OEIS

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

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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.