Sigma Interpretation: f(x)=X^2, j=1, n=4

[neotriz]

I just need a quick clarification on how to read this function

f(x) = sigma of X^2, starting at j=1, and n

so does that mean that f(3) would equal to 36, if n=4?

 

[neotriz]

I forgot to mention that this is a DeJong Equation, and I need to implement in the matlab

 

[elibj123]

Are you sure this is the function:

$$f(x)=\sum^{n}_{j=1}x^{2}$$

The term is independing of the sum, so the function is just:

$$f(x)=nx^{2}$$