User blog comment:Mh314159/A new approach, and a typography question/@comment-34422464-20190701005428/@comment-32213734-20190701024638

I often see instead of LaTeX expressions theirs source code. Ctrl+F5 sometimes helps. Now I see that your first expression works (I see "$fnn(a)$" with other font), but the second does not (I see "$ $f_n^n (a)$ $").