Ok this may be a simple task but I have a list of names some being duplicates however I wanted to know if there was any way to insert a blank row between each different name after alphabetizing everything in the first column. It would be similar to this:

Smith
Smith
Smith
Thomas
Thomas
Walker
Walker

And I need it to look like this

Smith
Smith
Smith
*blank row*
Thomas
Thomas
*blank row*
Walker
Walker

I have about 20k rows so going 1 by 1 would take forever. Any help would be much appreciated. Thank you.