For the recurrence an=an−1+2an−2a_n = a_{n-1} + 2a_{n-2}an=an−1+2an−2 with initial conditions a0=1a_0 = 1a0=1 and a1=3a_1 = 3a1=3, compute a3a_3a3.
a3=9a_3 = 9a3=9
a3=11a_3 = 11a3=11
a3=13a_3 = 13a3=13
a3=15a_3 = 15a3=15