I got the routine 3.
I clicked on the Add-Vent game that seems like it has a game for the 25 days until "Chrismaths".
I just picked 1 for December 1st, but you may be able to pick others.
The rules supposedly allow for exponents(^), factorials(!), and decimals(.).,
My game had 6 spaces and they started it with
the word BAUBLE which translated to something like 647618I got a 3 there as well.
Somebody pick something besides Day 1 and see if you get a different puzzle.
EDIT to add link:
https://www.nerdlegame.com/advent/index.html