A semi-popular mathematical puzzle/truth which states that all the integers between zero and 100 can be described using four fours and assorted mathematical symbols. For instance:

0 = (4+4)-(4+4)
1 = (44)/(44)
2 = (4*4)/(4+4)
3 = (4+4+4)/4
4 = sqrt(4*4)*(4/4)
5 = sqrt(4*4)+(4/4)
6 = (4!/4)+4-4
7 = (44/4)-4
8 = 4*4-4-4
9 = 4+4+(4/4)
10 = (4/.4)-4+4

One's effectiveness at solving these puzzles as the integers get larger depends in large part on one's creativity and mathematical vocabulary. Or else their ability to program a computer to do the dirty work for them.