When can you reconstruct the power series of a function by taking the limits of the coefficients of the polynomials that interpolate its values at $0,1,2,\dots,j$?
More precisely:
Let $f\colon\mathbb{R}\to\mathbb{R}$. For all nonnegative integers $j$, let $p_j$ be the unique polynomial of degree $j$ with real coefficients such that $p_j(n)=f(n)$ for $n=0,\dots,j$. Let $a_{j,k}$ be the coefficient of $x^k$ in $p_j$, where $a_{j,k}=0$ if $k>j$. Under what circumstances do we have that $\lim_{j\to\infty} a_{j,k}$ exists for all $j$? In this case, let $c_k=\lim_{j\to\infty} a_{j,k}$. When $f$ is analytic, under what circumstances do we have that $f(x)=c_0+c_1 x+c_2 x^2 + c_3 x^3 +\cdots$?