I only have two ideas, neither one of which is going to be terribly good news. The first idea is to attempt a series solution. Before doing so, you might want to transform the equation thus: let implying that Then and the DE becomes
It might be easier to work with the series solution in this format than with the equation.
The second idea is to solve the DE numerically. You'll need an initial condition to pull that off.
What is the context for this DE? Does it arise from a physical problem?