See the below image.
The Formula
="Days " & SEQUENCE(100, 1, 1)
The above Excel formula will write days with number in a "sequence" from 1 to 100. So, it wil fill hundred rows with the days number.
SEQUENCE() Function
The SEQUENCE() returns a sequence of number. Its a newly added function and its only avilable in Microsoft 365, Excel 2021 and Excel for the Web.
Here's the syntax.
The function takes "four" paramters.
1) rows - the number of rows to fill
2) columns - the number of columns to fill. Use this option if you want to fill values in multiple columns.
3) start - the starting number in sequence. This is optional
4) step - the increment between each number in the sequence.