This is cool.

Also, quick grammar lesson because I'm an English teacher who hasn't been able to really teach for 3 months and I'm having withdrawals:

"an" only goes before a word that makes a vowel sound, and y doesn't count as one of those. That is, the y as in "yeah" or "you", doesn't count as a vowel sound that needs an "n". A lot of people are taught that if the word following the a/an starts with a vowle it needs an "n," but that's technically not true (though its an easier golden rule for children to follow). It's based only on the sound that follows. Which is why I've been putting an n when I saw "an n", because we pronounce the letter "n" like "in" with the vowel sound from "i".

So this should be "a Euler". It could also be a simple typo and I'm wasting my breath here, but as I said...withdrawals.