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A227798 Number of composites removed in each step of the Sieve of Eratosthenes for 10^9. 3
499999999, 166666666, 66666666, 38095237, 20779220, 15984016, 11282834, 9501331, 7435826, 5640969, 5095068, 4131143, 3627360, 3374293, 3015292, 2616982, 2306411, 2192860, 1963654, 1825278, 1750219, 1595163, 1499127, 1381337, 1253379, 1191536 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) = the number of composites <= 10^9 for which the n-th prime is the least prime factor.

pi(sqrt(10^9)) = the number of terms of this sequence.

The sum of a(n) for n = 1..3401 = A000720(10^9) + A065855(10^9).

LINKS

Eric F. O'Brien, Table of n, a(n) for n = 1..3401

EXAMPLE

a(1) = 10^9 \ 2 - 1.

a(2) = 10^9 \ 3 - 10^9 \ (2*3) - 1

a(3) = 10^9 \ 5 - 10^9 \ (2*5) - 10^9 \ (3*5) + 10^9 \ (2*3*5) - 1

a(4) = 10^9 \ 7 - 10^9 \ (2*7) - 10^9 \ (3*7) - 10^9 \ (5*7) + 10^9 \ (2*3*7) + 10^9 \ (2*5*7) + 10^9 \ (3*5*7) - 10^9 \ (2*3*5*7) - 1.

CROSSREFS

Cf. A133228, A145538-A145540, A227155, A227797, A227799, A145532-A145537.

Sequence in context: A287550 A216011 A101641 * A234063 A210155 A203261

Adjacent sequences:  A227795 A227796 A227797 * A227799 A227800 A227801

KEYWORD

nonn,fini,full

AUTHOR

Eric F. O'Brien, Jul 31 2013

STATUS

approved

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Last modified January 27 01:45 EST 2021. Contains 340443 sequences. (Running on oeis4.)