Steps to be followed. Thats how to create sequence in Excel 365 with formulas. Therefore you wont find any of those functions in pre-dynamic Excel such as Excel 2019 Excel 2016 and lower.
Select the full data set.
Directly below the list add the full range again for example 1-10. Select the fill handle on the bottom right of the A1 cell and drag. Add full range of numbers. To add several numbers that are located in a single column or row in a worksheet use the SUM function which offers a shortcut to creating a long addition formula.