Let $f(x)$ be a function such that for all $x,$ $f(x) = f(x + 1) + f(x - 1).$  Given that $f(15) = 20$ and $f(20) = 15,$ compute $f(20152015).$
Question:
Let $f(x)$ be a function such that for all $x,$ $f(x) = f(x + 1) + f(x - 1).$  Given that $f(15) = 20$ and $f(20) = 15,$ compute $f(20152015).$
Answer:
Let's think step by step.

user
-5
Let $f(x)$ be a function such that for all $x,$ $f(x) = f(x + 1) + f(x - 1).$  Given that $f(15) = 20$ and $f(20) = 15,$ compute $f(20152015).$
train