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The rows of an Excel sheet are already numbered sequentially. The function ROW() returns the number of the row in which it is called. You can manipulate this number to show the number 1 in row 2. *=ROW()-1* and copy down.

In order to create a sequential number that increases every 10 rows you can use the *INT()* function. *INT()* returns the an integer calculated from an expression supplied as argument. For example,* INT(9/10)* = 0 but *INT(10/10)* returns 1, *INT(19/10)* = 1 etc.

The basic formula below returns 0 in rows 1 to 10, 1 in rows 11 to 20 etc.

`=INT(ROW()/10)`

To start counting from 1 modify the result.

`=INT(ROW()/10)+1`

To place the 1 in a row other than sheet row 1 deduct the row number in which you want to have the 1 from the row number. The formula below will place the number 1 in row 2.

`=INT((Row()-2)/10)+1`

Finally, to omit repeating numbers, use the *MOD()* function. It returns the unused remainder of a divison, the modulus. *MOD(9,10)* = 9 and *MOD(10,10)* = 0. The formula below returns a blank cell whenever the modulus isn't zero.

`=IF(MOD(ROW()-2,10),"",INT((ROW()-2)/10)+1)`

Note the peculiarity here: *IF(MOD(ROW()-2,10), [True], [False])*. This expression is equivalent to *IF(MOD(ROW()-2,10)***<>0**, [True], [False]). The *<>0* can be omitted.