A sequence satisfies an=an−1+an−2a_n = a_{n-1} + a_{n-2}an=an−1+an−2. If a0=0a_0 = 0a0=0 and a1=1a_1 = 1a1=1, what is the sum ∑i=0nai\sum_{i=0}^n a_i∑i=0nai?
an+2−1a_{n+2} - 1an+2−1
an+1a_{n+1}an+1
an+2+1a_{n+2} + 1an+2+1
2an+1−an2a_{n+1} - a_n2an+1−an