Quote:
Originally Posted by wblipp
IIRC, Bob Silverman was working a list of a^{n} ± b^{n}.
For numbers close to this form with known interest in the factors, Richard Brent will take factors of a^{337}1, with a < 10,000 and the factors > 10^{9}.
At present he lists factors for only a from 2 to 10 and a=337.

I have done all 4^n  3^n for n <= 261
I have done some recent work on extending 3^n +/ 2^n to n = 400.
There are about 2 dozen composites left.