Sort numbers in strings

[Lucas]

Thanks for all.

Otherwise.

Is there any easy way to extract the strings missing from the series?

In the example:

ab1234/3:2
ab1234/3:3
ab1234/3:4
ab1234/3:5
ab1234/3:6
ab1234/3:7
ab1234/3:8
bc3234/2:1
ch8218/5:1