computing hex digits of pi is fairly trivial, but decimal digits are not
For some definition of "fairly trivial", yes.
The Nth hexadecimal (or binary) digit of Pi can be computed in O(log N) space and O(N (log N)^2 log log N) time, while the best known algorithm for computing the Nth decimal digit requires O(N) space and O(N (log N)^2) time. This is due to Pi being expressible as a polylogarithm ladder in base 1/2 but not in base 1/10 (as far as we know).
computing hex digits of pi is fairly trivial, but decimal digits are not
For some definition of "fairly trivial", yes.
The Nth hexadecimal (or binary) digit of Pi can be computed in O(log N) space and O(N (log N)^2 log log N) time, while the best known algorithm for computing the Nth decimal digit requires O(N) space and O(N (log N)^2) time. This is due to Pi being expressible as a polylogarithm ladder in base 1/2 but not in base 1/10 (as far as we know).