MATLAB: How to process equation in summation

Question

i have a code kindly tell how to process,the signal is a sine signal and i want to process as like the equation in the image

Answer 1

Tl = 0; % initilization of summation
alphaNs = 2;
for k = 01:alphaNs
    Tl = Tl + abs(x(k)^2);
end
Tl = (1/alphaNs)*Tl;