This article describes the formula syntax and usage of the SERIESSUM function (function: A prewritten formula that takes a value or values, performs an operation, and returns a value or values. Use functions to simplify and shorten formulas on a worksheet, especially those that perform lengthy or complex calculations.) in Microsoft Excel.
Description
Many functions can be approximated by a power series expansion.
Returns the sum of a power series based on the formula:
Syntax
SERIESSUM(x, n, m, coefficients)
The SERIESSUM function syntax has the following arguments (argument: A value that provides information to an action, an event, a method, a property, a function, or a procedure.):
 X Required. The input value to the power series.
 N Required. The initial power to which you want to raise x.
 M Required. The step by which to increase n for each term in the series.
 Coefficients Required. A set of coefficients by which each successive power of x is multiplied. The number of values in coefficients determines the number of terms in the power series. For example, if there are three values in coefficients, then there will be three terms in the power series.
Remark
If any argument is nonnumeric, SERIESSUM returns the #VALUE! error value.
Example
The example may be easier to understand if you copy it to a blank worksheet.
How do I copy an example?
 Select the example in this article. If you are copying the example in Excel Online, copy and paste one cell at a time.
Important: Do not select the row or column headers.
Selecting an example from Help
 Press CTRL+C.
 Create a blank workbook or worksheet.
 In the worksheet, select cell A1, and press CTRL+V. If you are working in Excel Online, repeat copying and pasting for each cell in the example.
Important: For the example to work properly, you must paste it into cell A1 of the worksheet.
 To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.
After you copy the example to a blank worksheet, you can adapt it to suit your needs.

A 
B 
Coefficients 

=PI()/4 

1 

=1/FACT(2) 

=1/FACT(4) 

=1/FACT(6) 

Formula 
Description (Result) 
=SERIESSUM(A2,0,2,A3:A6) 
Approximation to the cosine of Pi/4 radians, or 45 degrees (0.707103) 
