I believe you mean "describable by a polynomial formula", in which case the answer is "yes".

Given n terms ![s\sb 0, \cdots, s\sb {n-1}](http://latex.mathoverflow.net/png?s%5F0%2C%20%5Ccdots%2C%20s%5F%7Bn%2D1%7D), start with a polynomial of degree n:

![a\sb 1x^n+a\sb 2x^{n-1}+ \cdots + a\sb {n-1}x + a\sb n](http://latex.mathoverflow.net/png?a%5F1x%5En%2Ba%5F2x%5E%7Bn%2D1%7D%2B%20%5Ccdots%20%2B%20a%5F%7Bn%2D1%7Dx%20%2B%20a%5Fn)

Create a system of n equations such that for each polynomial where x = 0, .. , n-1 the polynomial is set equal to ![s\sb 0, \cdots, s\sb {n-1}](http://latex.mathoverflow.net/png?s%5F0%2C%20%5Ccdots%2C%20s%5F%7Bn%2D1%7D).

Solve the system of equations for all terms ![a\sb 1, \cdots, a\sb n](http://latex.mathoverflow.net/png?a%5F1%2C%20%5Ccdots%2C%20a%5Fn) and voila, a formula.

Now repeat the same thing for a polynomial of one higher degree, dropping the ![a\sb {n-1}x](http://latex.mathoverflow.net/png?a%5F%7Bn%2D1%7Dx) term so there are still n terms in total.

Voila, a second formula.