[EMAIL PROTECTED] writes:
So, is this:
(2^p mod f) - 1
Congruent to this:
(2^p -1) mod f
Yes, though be careful about the case of 2^p mod f being 0. The first
will give you -1 and the second is f-1. They are congruent, mod f, of
course, but not identical.
This is doubly great, because TI-92s can go up to 614 decimal digit
precision, so I can store the entire factor.
So you should be able to test factors up to about 307 digits. Not
bad.:)
I am completely and utterly C illiterate. Mathematical ranting makes more
sense. BASIC is also good. But it doesn't matter, because I have a TI-92
function already that does a^b mod c.
It's probably the same algorithm; it's quite well known. (Though I
didn't know about it until George pointed it out to me when I joined
GIMPS back in Jan. of 1996; sped up my pre-GIMPS factorer by a factor
of three!).
If this is correct, I will craft a TI-92 program immediately to
factor Mersenne numbers. *drool drool* An untapped source of
computing power exists. Even if we can't factor up to 2^62 like
larger computers can, TI users will be able to scan low
factors. Not sure how fast, though. Yippee!
Actually, you can go farther; 2^62 is only about 20 digits. But
perhaps too slowly, as you note in a later message. And the mers
package programs can factor arbitrarily far, but also slower than
George's programs.
<<However, I cannot think of any way to do an LL test without
storing the number in memory. Is there way?>>
Neither can I. And TIs don't have 4MB RAM. *sob*.
As I've (just) pointed out, the LL test doesn't need the Mersenne
number itself either. However, it does need numbers just as large,
which is what prevents doing LL on TIs.
Will
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