How Many ? (Posted on 2004-01-02)

	Submitted by Ravi Raja
Rating: 2.6667 (9 votes)
Solution:	(Hide)
2^(3) = 1 (mod 7). Hence 2^(3m) = 1 (mod 7), 2^(3m+1) = 2 (mod 7), and 2^(3m+2) = 4 (mod 7). Hence we never have 7 dividing 2^n + 1, and 7 divides 2^n - 1 iff 3 divides n.

	Subject	Author	Date
	Puzzle Solution	K Sengupta	2021-12-23 08:45:40
	No Subject	K Sengupta	2008-02-07 05:14:03
	re: la meme Janette mais autrement coifee!	mark hartman	2004-01-29 18:42:49
	solution	mark hartman	2004-01-29 18:34:50
	la meme Janette mais autrement coifee!	luminita	2004-01-08 09:56:07
	Brute force	Dan Blume	2004-01-02 16:44:11
	Solution	Richard	2004-01-02 10:51:26