plotting instead of sketching

[Thomas Nutz]

Dear Professor,

can we plot the sum of some series elements or do you want us to draw it by hand?

[Victor Ivrii]

Whatever. In fact if I have time I do both: if there are too different I try to understand who (me or the plotter) is mistaken (or may be both be correct and wrong in the same time). Look here

http://weyl.math.toronto.edu:8888/forum244-2011S/index.php?topic=48.msg159#msg159