That subject was introduced in the forum a while ago. I was clear about difficult
in Mathcad equipped for, though not so easy either, but done well manually.
As you can see, the task consists in collecting the C's of equal power of 'x'
Then solving for each 'C' as solution to Frobenius.

ODE Frobenius.sm (171 KiB) downloaded 40 time(s).

Borrowing the C's equalities from Mathcad, Smath solves.
But by itself, I have abandoned Smath Frobenius.