If I understood correctly:
numerators = t - repmat(et(:), 1, numel(et)); %calculate t-et(1), t-et(2), etc.
numerators(logical(eye(size(numerators)))) = 1; %replace t-et by 1 on diagonal
numerators = prod(numerators);
denominators = et - et';
denominators(logical(eye(size(denominators)))) = 1;
denominators = prod(denominators);
result = sum(numerators ./ denominators);
However, the result of this is always going to be 1. So
result = 1;
may be simpler.
