Let $\lambda_n$ be an increasing and unbounded sequence of positive real numbers and $a_n$ be a sequence of real numbers such that
$$\sum \limits_{n=1}^{\infty} a_n \lambda_n^{k}=0 \ \ \hbox{for all}\ \ k\geq 0.$$$$\sum_{n=1}^\infty a_n \lambda_n^k=0 \ \ \text{ for all }\ \ k\geq 0.$$
Is $a_n=0$ for all $n$?