Interesting scenario -

I have a spreadsheet with one column - 35,000 unique item numbers

Example:

item a
item b
item c
item d
item e

I need to duplicate each row - making a spreadshhet with one column 70,000 rows as such:

item a
item a
item b
item b
item c
item c
item d
item d
item e
item e

I tried a formula - couldn't come up with anything - looked for some kind of merge type functionality - did find anything........

Any guidance would be appreciated........