Help with discrete math proof I'm having trouble with the following:
$\ a_1=1$ and $a_n=1+\sum_{i=1}^{n-1} a_i$ for $n>1$
How should I go about proving the below? Any hints?
$a_n = 2^{n-1}$

Induction is ugly xd
$$
a_n-a_{n-1}=\left(1+\sum_{i=1}^{n-1}a_i\right)-\left(1+\sum_{i=1}^{n-2}a_i\right)=a_{n-1}
$$
Considering that $a_1=2^0$ then $a_n=2^{n-1}$.
