There were 2 codes in the Citadel post on the Investigate Blog.
[1] 012345565667654432110-1-2-100-1-2-1-101233210012332234554567887676654567789×99
[2] dkzrxthtesmlytsirubm
Code #1
Observations
The numbers seem to be somewhat in increasing or decreasing order, but there are weird symbols around some of the numbers (- and ×).
[hint]
The dashes are next to 1, and 2, which means negative numbers, and it makes sense since it would be decreasing from 0.
The × next to the 9 probably means a 10 (Roman Numeral).
[/hint]
Code #2
Observations
The length of the code is 20 characters, which is below average for a string with 4 numbers. Transposition doesn’t give us anything useful.