login
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
OFFSET
1,1
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
KEYWORD
nonn,less
AUTHOR
EXTENSIONS
Corrected by R. J. Mathar, Jul 12 2011
STATUS
approved