Autofill cells with a formula Sequence

I have a simple formula in Cell C2;

=SUM(A1+15000)-A1

I would like calc to auto fill the formula+1 for the selected cells (C2:C270)

like this

Cell C3;
=SUM(A1+15000)-A2
Cell C4;
=SUM(A1+15000)-A3
Cell C5;
=SUM(A1+15000)-A4

Is there any way to do this?

Thank you

-1- Learn about absolute vs relative addressing.
=SUM(A$1+15000)-A2 ‘Sheet’ > ‘Fill Cells’ > ‘Down’ (Ctrl+D) or drag fill handle with the mouse.

-2- For what reason that contrived formula? Use =A$1-15000-A2 or similar.