The BESSELJ function returns the Bessel function Jn(x).
Syntax: =BESSELJ(X, N)
The BESSELJ function syntax has the following arguments:
 x: required. This is the value at which to evaluate the function
 n: also required. This represents the order of the Bessel function. If n is not an integer, it is truncated accordingly.
Example: Let’s look at some Excel BESSELJ function examples and explore how to use the BESSELJ function as a worksheet function in Microsoft Excel:
Syntax: =BESSELJ(A2,B2)
Result:
Based on the Excel spreadsheet above, the following BESSELJ examples would return:
Syntax: =BESSELJ(A3,B3)
Result: 0.114903485
Syntax: =BESSELJ(A4,B4)
Result: 0.576724808
Syntax: =BESSELJ(A5,B5)
Result: 0.576724808
Syntax: =BESSELJ(A6,B6)
Result: 0.477685497
Syntax: =BESSELJ(A7,B7)
Result: 0.352834208
Syntax: =BESSELJ(A8,B8)
Result: 0.329925829
Syntax: =BESSELJ(A9,B9)
Result: 0.557936508
Syntax: =BESSELJ(A10,B10)
Result: #NUM!
Note:
 If x is nonnumeric, BESSELJ returns the #VALUE! error value.
 If n is nonnumeric, BESSELJ returns the #VALUE! error value.
 If n < 0, BESSELJ returns the #NUM! error value.

The nth order Bessel function of the variable x is: where: is the Gamma function