4
votes
3answers
731 views

Chameleons Riddle

There are 10 red, 11 blue, 12 green chameleons. Sometimes, two chameleons meet. If they are the same color, nothing happens. If they are different colors, they will both change to the third ...
2
votes
0answers
82 views

When does $n^2$ divide $2^n+1$? [duplicate]

Possible Duplicate: How many rationals of the form $\large \frac{2^n+1}{n^2}$ are integers? A friend of mine asked me this question over lunch, and it's been a week that I can't do ...
1
vote
1answer
142 views

A rule to determine the crossed out digit

Lets take any integer, $z=abc\cdots$, form the sum of its digits, $a+b+c+\cdots$, subtract this from $z$, cross out any one digit from the result, and denote the sum of the remaining digits by $w$. ...