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A192393 Number of primes in the half-open interval [semiprime(n)-sqrt(semiprime(n)), semiprime(n)). 1
2, 1, 1, 1, 2, 1, 2, 1, 1, 1, 2, 2, 1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 1, 1, 1, 3, 4, 3, 2, 2, 1, 1, 1, 1, 2, 2, 3, 3, 2, 2, 2, 2, 3, 3, 3, 2, 3, 2, 2, 3, 3, 2, 3, 4, 4, 4, 4, 3, 2, 2, 1, 1, 1, 1, 1, 1, 2, 4, 4, 3, 2, 3, 3, 2, 2, 3, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..86.

FORMULA

Conjecturally, a(n) ~ sqrt(n log log n / (log n)^3). - Charles R Greathouse IV, Jun 29 2011

EXAMPLE

a(1)=2 because 2 and 3 are in range [semiprime(1)-sqrt(semiprime(1)), semiprime(1))=[2, 4).

MAPLE

A192393 := proc(n) local phi, plo;  phi := A001358(n)-1 ; plo := ceil(A001358(n) -sqrt(A001358(n)))-1 ; numtheory[pi](phi)-numtheory[pi](plo) ; end proc: # R. J. Mathar, Jul 12 2011

CROSSREFS

Cf. A001358.

Sequence in context: A242481 A228287 A213636 * A184303 A218545 A205600

Adjacent sequences:  A192390 A192391 A192392 * A192394 A192395 A192396

KEYWORD

nonn,less

AUTHOR

Juri-Stepan Gerasimov, Jun 29 2011

EXTENSIONS

Corrected by R. J. Mathar, Jul 12 2011

STATUS

approved

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Last modified September 28 21:27 EDT 2020. Contains 337393 sequences. (Running on oeis4.)