245
xkcd #2937: Room Code
(imgs.xkcd.com)
Alt text:
Sorry to make you memorize this random string of digits. If it helps, it can also double as a mnemonic for remembering your young relatives' birthdays, if they happened to have been born on February 5th, 2018.
I do these all the time.
This one is a bit trickier than usual but thinking 2, 5 and a number that adds up to 8.
02 + 05 + ? = 8
The sequence of 2, 5, 8 is also very nice since you get the subsequent numbers by adding 3s
Oh man, there's more than one of us