this is the forum space for the tool SQL Developer. As the title clearly says it is (Not for general SQL/PLSQL questions).
Please post your question in SQL & PL/SQL
When posting there you should explain your business case, this means: What do you want to do.
making my select statement run three times
Do you want to run the same statement three times? Three times with a pause in between? What do you want to do with the result?
Also a sequence is only there to generate numbers. It's not there to control the execution of a statement.