Nice article and cute problems . In the text of the first additional problem there is a small typo, I think you meant palindromic substrings, not subsequences (I think everybody understood substrings anyway ).
P.S.: Oh, and while I'm still in the bitchin' mode: I had an issue while viewing comments on the blog page after logging in: it says "Continutul nu poate fi descarcat". It seems to happen when using the https protocol (the browser isn't very happy about performing an AJAX request to an unsecured location). Sorry for the digression.