In my institution I have a friend who is part of this Math club where they write blog posts and share them online at medium.com. However, there is an issue with my friends post.After they shared it with me to go through, check for errors and edit, I looked online and found this. My issue is that their working and explanations are all copied from the person who wrote this, my friend has only changed a few words(5-10). I am worried that if they post this they will get into a lot of trouble since plagiarism is dealt with very harshly in my institution. However, they denied copying from there. I don't mean to sound rude, but I do not believe them. How should I go about this? Should I report them? FYI: There were no citations in their article.
There is no way to know the provenance of the information found in the online blog that was the suspected source. Several people have written about this odd mathematical series, including Wolfram. Your friends may have been trying to efficiently summarize, as best they could, the considerable information they found in attempting to educate others and clarify this rather strange mathematical series which adds to -1/12. Is there any way to claim that a math instructor's class lecture notes doing the same thing would be called plagiarism? Well, probably not. Nevertheless, someone may wish to argue the issue depends on one's view of the situation.