loop through column and copy instances of text

Sorry, that didn't sound too clear. Row A (Sheet 1) has a list of serial numbers (alphanumeric). I'm looking to be able to loop through that row and copy a list of the numbers as in the example below but can't figre out how to do it. Any help appreciated.

Row A
a2314
a2314
b345
b346
a2314
b346
c478

So what will be copied in a new row is:
a2314
b345
b346
c478