To find the sum of a sequential integer range in Excel, you can use the **SUM** function. This function takes two arguments: the first is the cell containing the first number in the range, and the second is the cell containing the last number in the range. For example, if you wanted to sum the numbers 1 through 10, you would use the following formula:

`=SUM(A1:A10)`

This would return 55, since 1+2+3+4+5+6+7+8+9+10 = 55.

You can also use the **SUM** function to sum non-contiguous ranges of cells. For example, if you wanted to sum the numbers 1, 3, 5, 7, and 9, you could use the following formula:

`=SUM(A1,A3,A5,A7,A9)`

This would also return 55.