Expansion of generating function $\frac{1}{ \sqrt{1-12x+4x^2 } }$ I came across this generating function
$$\frac{1}{ \sqrt{1-12x+4x^2 } }$$
How exactly does one expand this series? I have read through some notes, it seems like we need to factorize the denominator, but it doesn't look like this one can be factorized?

Make the long division
$$\frac{1}{ 1-12x+4x^2  }=1+12 x+140 x^2+1632 x^3+19024 x^4+221760 x^5+2585024 x^6+O\left(x^7\right)$$
Now (being patient), the binomial expansion
$$\frac{1}{ \sqrt{1-12x+4x^2 } }=1+6 x+52 x^2+504 x^3+5136 x^4+53856 x^5+575296 x^6+O\left(x^7\right)$$
