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A072114 Number of 3-almost primes (A014612) <= n. +0
3
0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 4, 4, 4, 4, 4, 4, 4, 5, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 9, 10, 10, 10, 10, 10, 11, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 13, 13, 13, 14, 14, 15, 15, 16, 16, 16, 16, 16, 17, 18, 18, 19, 19, 19, 19, 19, 19, 19 (list; graph; listen)
OFFSET

0,13

COMMENT

Number of k <= n such that bigomega(k) = 3.

Let A be a positive integer then card{ x <= n : bigomega(x) = A } ~ (n/Log(n))*Log(Log(n))^(A-1)/(A-1)!. For which n, card{ x <= n : bigomega(x) = 3 } >= card{ x <= n : bigomega(x) = 2 } ?

REFERENCES

E. Landau, Handbuch der Lehre von der Verteilung der Primzahlen, vol. 1, Teubner, Leipzig; third edition : Chelsea, New York (1974).

G. Tenenbaum, Introduction \`a la th\'eorie analytique et probabiliste des nombres, p. 203, Publications de l'Institut Cartan, 1990.

FORMULA

a(n) = card{ x <= n : bigomega(x) = 3 }, asymptotically : a(n) ~ (n/log(n))*log(log(n))^2/2 [Landau, p. 211]

PROGRAM

(PARI) for(n=1, 100, print1(sum(i=1, n, if(bigomega(i)-3, 0, 1)), ", "))

CROSSREFS

Cf. A014612, A109251, A001358, A072000.

Sequence in context: A092670 A120450 A127238 this_sequence A090621 A029378 A053278

Adjacent sequences: A072111 A072112 A072113 this_sequence A072115 A072116 A072117

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre (benoit7848c(AT)orange.fr), Jun 19 2002

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.


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