Summation with looping for each value of n

[Excelenjoyer1]

Hello,

I need to find the value of "Q" for each value of "n" for example; if the value of "n" is 12 then numbers from 1 to 12 should be added to the formula below 

the real formula is as the following:

Q=(1+2*(cos(n1*B))^(5/2)+2*(cos(n2*B)^(5/2) + ... +2*(cos(n*B))^(5/2))

and the "n" is determined by; ((z-1)/4)

how can i achieve this result?

Thank you in advance,

[#2]

@Excelenjoyer1 

You have a problem here: for some values of i = 1, 2, ..., n, COS(i*B) will be negative, so COS(i*B)^(5/2) will return #NUM!