In this post, I prove the inequalities
log2⋅x−3logx≤ψ(x)≤2log2⋅x+3log2log2x
for all real x≥2. Hereby is ψ(x)=∑n≤xΛ(n)
with Λ the von Mangoldt function. This is a second post motivated by Chebyshev's paper "Mémoire sur les nombres premiers" from 1852. In this paper, Chebyshev uses a more complex variant of the calculation below to obtain stronger inequalities. Similar inequalities can also be found on page 50 in Murty's book.
Wednesday, August 26, 2015
Sunday, August 23, 2015
How not to prove Bertrand's postulate
This is a first post motivated by Chebyshev's paper "Mémoire sur les nombres premiers" from 1852. In this paper Chebyshev proves Bertrand's postulate that there is always a prime between a and 2a for all a≥2. Chebyshev bases his proof on inequalities for the function
T(x)−T(x2)−T(x3)−T(x5)+T(x30)
with
T(x)=∑1≤n≤xlogn
Chebyshev's paper is quite easy to read and can be found at this link. In this post I will follow Chebyshev's reasoning on an easier version of (2).
Subscribe to:
Posts (Atom)