First digits of extremely large numbers (Generalization of "first digits of Graham's number")

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I found a question about the first digits of Graham's number and would like to generalize it :

We want the first n digits of the number $a\uparrow^b c$.

  • Which method is the most effective to do that ?
  • For which magnitude of a,b,c is the calculation feasible ?
  • Is there a hope to calculate at least the first digit of Graham's number ?

If the only way to find the first digits is to simply calculate the number, then already $3\uparrow \uparrow \uparrow 3$ would be out of reach.

I tried to find out some patterns of the leading digits of powers, but there seems to be no structure.

I know, that this question is somewhat broad, nevertheless I hope for some useful hints.