i=1 ===> j loop runs log (1) times

i=2 ===> j loop runs log (2) times

i=3 ===> j loop runs log (3) times

......

i=n ===> j loop runs log (n) times

Total time runs = log(1) + log(2) + ....+ log(n) = log (1.2.3.4.....n) = log (n!) = log(n^{n}) = n.log(n)