When you need to continue a pattern for an entire column or row, Autofill will complete this task quickly. To use Autofill, select cells to use as a source. Drag the lower right corner of the selection to the cells that you want to copy to.

If there is a numerical pattern, that pattern will be continued. Otherwise, the cells will be copied from the source cells. The lower right icon after Autofill shows options to change the fill result: Copy Cells, Fill Series, or Flash Fill.