let P(x):= sum_(p leq x) Log [p] , then we have P(2^(k+1))=sum_(i=0)^k(P(2^(i+1))-P(2^i))<2*Log[2]*(1+2+4+...+2^k)<=4*Log[2]*2^k Why does this equation work? The first step is clear for me, since we have a telescope sum. However, how can I conclude to the first < and the <=?

Kaydence Villegas

Kaydence Villegas

Open question

2022-08-20

Why does this equation work?
let P ( x ) := p x L o g [ p ], then we have
P ( 2 k + 1 ) = i = 0 k ( P ( 2 i + 1 ) P ( 2 i ) ) < 2 L o g [ 2 ] ( 1 + 2 + 4 + . . . + 2 k ) 4 L o g [ 2 ] 2 k
Why does this equation work?
The first step is clear for me, since we have a telescope sum. However, how can I conclude to the first < and the ?

Answer & Explanation

Drew Patel

Drew Patel

Beginner2022-08-21Added 9 answers

The problem is solved now, the solution is pretty simple, since
P ( 2 n ) P ( n ) < 2 L o g [ 2 ] n
which can be shown fast, we can conclude the above inequality by setting
2 n = 2 i + 1 and n = 2 i + 1 / 2 = 2 i and then summing up.
Thanks for your help.

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