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Algebra Difficulty 4.8 AIME Find the answer

For the sequence of numbers n1,n2,n3,n_{1}, n_{2}, n_{3}, \ldots, the relation ni=2ni1+an_{i}=2 n_{i-1}+a holds for all i>1i>1. If n2=5n_{2}=5 and n8=257n_{8}=257, what is n5n_{5} ?

A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

Solution

33.

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