For the recurrence an=2an−1+an−2a_n = 2a_{n-1} + a_{n-2}an=2an−1+an−2 with positive initial conditions, what is limn→∞an+1an\lim_{n \to \infty} \frac{a_{n+1}}{a_n}limn→∞anan+1?
1+52\frac{1+\sqrt{5}}{2}21+5
1+21 + \sqrt{2}1+2
222
1+31 + \sqrt{3}1+3