Can this be solved with any HP CAS?

[AlexFekken]

(09-27-2017 04:25 PM)Nigel (UK) Wrote:  It doesn't take long with pencil and paper either!

In case anyone is interested in such a calculator-less solution:

2^6 = 64 = -1 (because 65 = 5 * 13)
Squaring that gives 2^12 = 1
This means 2^1000 = 2^(1000 mod 12) = 2^4 = 3

(all calculations are "mod 13" of course)