OFFSET
1,3
COMMENTS
Number of primes in the interval ]sqrt(n), n], (i.e., excluding sqrt(n) but including n). - Lekraj Beedassy, Mar 31 2005
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..1000
FORMULA
EXAMPLE
n=100, lcm(100) has 25 prime factors of which only 2 and 3 have exponent larger than 1; resulting powers: 64 and 81. So 23 prime factors are unitary, i.e., with exponent 1, so a(100)=23.
MATHEMATICA
Join[{0}, Table[Count[Transpose[FactorInteger[Product[Cyclotomic[k, 1], {k, 2, n}]]][[2]], 1], {n, 2, 100}]] (* G. C. Greubel, May 13 2017 *)
PROG
(PARI) for(n=1, 100, print1(primepi(n) - primepi(sqrt(n)), ", ")) \\ G. C. Greubel, May 13 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Aug 28 2000
STATUS
approved