maybe I didn't understand (my english is not so good).
do you want to find all integers between 1218 and 1253?
in this case you can copy and paste this string in grep find
This should do what you are looking for...
or this if you want to make sure there is nothing before and/or after the numbers
Although the two work well, I must admit that your version is more … attractive!
[error in the second code]
Attractive... ??! I never toughs that GREP could be attractive!
[I have fixed the error on the second grep ]