Which initial conditions make an=2an−1−an−2a_n = 2a_{n-1} - a_{n-2}an=2an−1−an−2 produce a constant sequence?
a1=5, a2=5a_1 = 5,\; a_2 = 5a1=5,a2=5
a1=0, a2=1a_1 = 0,\; a_2 = 1a1=0,a2=1
a1=1, a2=2a_1 = 1,\; a_2 = 2a1=1,a2=2
a1=2, a2=0a_1 = 2,\; a_2 = 0a1=2,a2=0