Is it true that $\limsup M_n=\infty$?
Is it true that there exists $c>0$ such that for infinitely many $n$ we have $M_n > n^c$?
Is it true that there exists $c>0$ such that, for all large $n$, \[\sum_{k\leq n}M_k > n^{1+c}?\]
Is it true that $\limsup M_n=\infty$?
Is it true that there exists $c>0$ such that for infinitely many $n$ we have $M_n > n^c$?
Is it true that there exists $c>0$ such that, for all large $n$, \[\sum_{k\leq n}M_k > n^{1+c}?\]
The second question was answered by Beck [Be91], who proved that there exists some $c>0$ such that \[\max_{n\leq N} M_n > N^c.\] The third question seems to remain open.