Merging data in 2 columns?

I have data in column A and column C. Starting at A3, I need to insert the data from C1, and then in A13 I need to insert the data in C2, then A23 insert data from C3, etc... I have to increase the formula by 10 rows in column A for every "copy data(=+C1)request to column C without having to increase the rows for column C. This is congruent data with no breaks, column A breaks every 10 rows starting with A3. Any suggestions???