I need to write matlab code for euclid's method for BCH decoding, but i don't know how to calculate syndrome for the method using matlab?

I need to write matlab code for euclid's method for BCH decoding, but i don't know how to calculate syndrome for the method using matlab? r(x) = 1 + x^17+ x^28, t=2, syndrome will be s = [ a^2, a^4, a^21, a^5] and GF[2^5]