Find the first few coefficients.

Find the radius of convergence

I get that R = 6 (which is correct) but I don't know how to find c_0 to c_4. What I think I need to do is isolate x^n and then the rest is the c stuff. So I got sigma from 0 to inf of (-1/6)^n * x^n so (-1/6)^n so, shouldn't that be by C_n values?

This is what I get (which is apparently wrong according to my school's computer system):

C_0 = (-1/6)^0 = 1

C_1 = (-1/6)^1 = -1/6

C_2 = (-1/6)^2 = 1/36

C_3 = (-1/6)^3 = -1/216

C_4 = (-1/6)^4 = 1/1296

Any help would be GREATLY appreciated!

Thanks in advance!