(In reply to re: Solution (spoiler)
When Wolfram Alpha is asked to evaluate
sum sin(k*x) / k^3,k=1 to infinity
1/2 i (Li_3(e^(-i x)) - Li_3(e^(i x)))
When it's asked to
plot 1/2 i (Li_3(e^(-i x)) - Li_3(e^(i x))), x=0 to 400
the graph seems to vary only between -1 and 1.
It seems to reach a local maximum of 1 at about 4003.7, for example, when plotting between x=4002 and 4005.
Posted by Charlie
on 2018-10-31 11:56:13