If [math] l^r{x} [/math] means [math]\log\log\log...\log{x}[/math], the log being repeated 'r' times. Then how do I prove that: [math]\int{{x.l(x).l^2(x)....l^r(x)}^{-1}}dx = l^{r+1}(x) + C[/math]?
valid question