OFFSET
1,1
COMMENTS
Let f(m) = number of semiprimes <m then a(n) is the number of semiprimes between 1+(n-1)*10^6 and n*10^6.
a(n) = 0 for almost all n. It seems infeasible to find the first such n. - Charles R Greathouse IV, Sep 09 2012
LINKS
Zak Seidov, Table of n, a(n) for n = 1..1000
FORMULA
a(n) ~ 1000000 n log log n / log n. - Charles R Greathouse IV, Sep 23 2012
MATHEMATICA
f[m_] := Sum[ PrimePi[(m - 1)/Prime[i]], {i, PrimePi[ Sqrt[m]]}] - Binomial[ PrimePi[ Sqrt[m]], 2]; ta=Table[f[n*10^6], {n, 0, 1000}]; s=Rest[ta]-Most[ta] (* for first 1000 terms *)
PROG
(PARI) a(n)=sum(k=10^6*(n-1), 10^6*n, bigomega(k)==2) \\ Charles R Greathouse IV, Sep 09 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Sep 09 2012
STATUS
approved