This doesn't look like a suitable case for regular expressions. You'd have to build a regex pattern containing every possible sequence to test for, because regex doesn't have a construct for comparing the difference between two characters within a match. It would probably be easier to implement this using a loop. Check each five-character substring from the input to see if it's contained within a string containing the letters in sequence, remembering to account for case and accents if required.
"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer
