Fill data automatically in worksheet cells in Microsoft Excel

Use the Auto Fill feature to fill cells with data that follows a pattern or are based on data in other cells.

1. Select one or more cells you want to use as a basis for filling additional cells.For a series like 1, 2, 3, 4, 5…, type 1 and 2 in the first two cells. For the series 2, 4, 6, 8…, type 2 and 4.For the series 2, 2, 2, 2…, type 2 in first cell only.
2. Drag the fill handle .
3. If needed, click Auto Fill Options    and choose the option you want.

Source:

https://support.microsoft.com/en-us/office/fill-data-automatically-in-worksheet-cells-74e31bdd-d993-45da-aa82-35a236c5b5db