Which command is similar with IsNull function in VBA for assign 0 when detect not assigned

(b0*z^n+b1*z^(n-1) + ... + bn) / (a0*z^n+a1*z^(n-1)+... + a_n_minus_m*z^m)

expand
into

beta0 + beta1*(1/z) + ... + betam*(1/z^m) + beta_m_plus_1*r_m_plus_1(z)/a(z) + ... + betan*rn(z)/a(z)

assume i have a number 26 and assume a prime number not greater than a value, let it be 5

then it is like a division and factor into 5^2 + 1

if prime number set to 17, then it will output 17 + 3^2, 

the output will be in terms of prime number, such as  a^3+b^2 + c  where a and b are prime number

it should start from greatest prime number given as a parameter in function

http://www.maplesoft.com/applications/view.aspx?SID=33040&view=html

it can calculate from numeric data, is it the end?

where do multiset coming from?

if given a multiset, and calculate its power sums, then i express this power sums in terms of symmetirc polynomials, what is the purpose of this?

http://www.mapleprimes.com/questions/144384-Polynomials-Not-In-The-Correct-Indeterminates

above link's comment said eliminate will NOT generate a polynomial in all cases

make me think that eliminate in above link can not return correct one.

what is the correct way to convert groebner basis of kernel into kernel?