Is there a function with the property$ f(n)=f^{(n)}(a)$ Is there a not identically zero, real-analytic function $f\colon\mathbb R\to\mathbb R$, which satisfies
$$f(n)=f^{(n)}(a),n\in\mathbb N \text{ or }\mathbb N^+?$$
and $a\in \mathbb R$
I saw a special case when $a=0$
I try to solve it by :
$$f(x)=e^{cx}$$
$$f(n)=e^{nc}$$
$$f^{(n)}(x)=c^ne^{cx}$$
$$f^{(n)}(a)=c^ne^{ca}$$
so $$e^{nc}=c^ne^{ca}$$
so $$c=\frac{nW(\frac{a-n}{n})}{a-n}$$
the problem is we always see  n with c 
but the special case when a=0 give 
$$c=\frac{nW(\frac{0-n}{n})}{0-n}$$
$$c=\frac{W(\frac{-1}{1})}{-1}=-W(-1)$$
I think there is no solution when $a\neq 0$
may be there is another function can solve it
Is there any solution in general?
thanks for all

I can't explicitly find an example, so perhaps turning to an existence proof, that can also be used to construct an example. To do so, consider the operator $\mathcal L_a: C^\infty \times \mathbb N \to \mathbb R$, where $\mathcal L_a\{f,n\} = f(n) - f^{(n)}(a)$. Then inspect Banach fixed-point theorem, if you can choose a norm in $C^\infty \times \mathbb N$ where $\mathcal L_a$ is a contraction, then jack-pot. Or, if it is not a contraction, for many reasonable norms, then you can say there is probably no such function in Banach space.
Hope this helps.
