1/1-1/2+1/2-1/3+1/3-1/4+...+1/n-1/(n+1) >2015/2016
1-1/(n+1)>2015/2016
n/n+1>2015/2016....cum 2015/2016=2015/2016⇒
2016/2017>2015/2016
(poti verifica) prin calcul direct 2016²>2015*2017=(2016-1)(2016+1)=2016²-1²
n minim=2016
