Now that you have proposed a fake post for the HC
2 Facebook page, Heidi wants to measure the quality of the post before actually posting it. She recently came across a (possibly fake) article about the impact of fractal structure on multimedia messages and she is now trying to measure the self-similarity of the message, which is defined as
where the sum is over all nonempty strings
p and
is the number of occurences of
p in
s as a
substring. (Note that the sum is infinite, but it only has a finite number of nonzero summands.)
Heidi refuses to do anything else until she knows how to calculate this self-similarity. Could you please help her? (If you would like to instead convince Heidi that a finite string cannot be a fractal anyway — do not bother, we have already tried.)