Find formula from values Is there any "algorithm" or steps to follow to get a formula from a table of values.
Example:
Using this values:
X                Result
1                3
2                5
3                7
4                9

I'd like to obtain:
Result = 2X+1

Edit
Maybe using excel?
Edit 2
Additional info:
It is not going to be always a polynomial and it may have several parameters (I think 2).

(This is way too complicated to use it here, one can always expect a desired polynomial that fits all the points.)
One of the possible algorithm is Langrange Interpolating Polynomial.
For a polynomial $P(n)$ of degree $(n-1)$ passes through $n$ points: 
$$(x_1,y_1=f(x_1)),\ldots,(x_n,y_n=f(x_n))$$
We have
$$P(x)=\sum_{j=1}^n\left[y_j\prod^n_{k=1,k\neq j}\frac{x-x_k}{x_j-x_k}\right]$$
Explicitly,
$$P(x)=\frac{y_1(x-x_2)\cdots(x-x_n)}{(x_1-x_2)\cdots(x_1-x_n)}+
\frac{y_2(x-x_1)(x-x_3)\cdots(x-x_n)}{(x_2-x_1)(x_2-x_3)\cdots(x_2-x_n)}+\ldots
+\\\frac{y_n(x-x_1)\cdots(x-x_{n-1})}{(x_n-x_1)\cdots(x_n-x_{n-1})}$$
In this context,
\begin{align}
P(n)&=\frac{3(n-2)(n-3)(n-4)}{(1-2)(1-3)(1-4)}+\frac{5(n-1)(n-3)(n-4)}{(2-1)(2-3)(2-4)}\\
&+\frac{7(n-1)(n-2)(n-4)}{(3-1)(3-2)(3-4)}+\frac{5(n-1)(n-2)(n-3)}{(4-1)(4-2)(4-3)}
\end{align}
Simplify and we get 
$$P(n)=-\frac13(2 n^3-12 n^2+16 n-15)
$$
