Here's a nice one called "3n+1" sequence. Take a random number and do

the following:

- if it is even, divide it by 2

- if it is uneven multiply it by 3 and add 1

Do this repeatedly and you'll always get to "1" The funny part is that there is no absolute proof for this rule, but

no-one has disproved it either. So far, each value taken as a start

value will end up being 1 in the end. Of course, the trick here is that

if you multiply an uneven number with 3 it will remain uneven. Add one,

it'll be even. So the final sequence will always be:

40-20-10-5-16-8-4-2-1 ... or does it? So, here's a try:

136 -> 68 -> 34 -> 17 -> 52 -> 26 -> 13 -> 40 -> 20 -> 10 -> 5 -> 16 ->

8 -> 4 -> 2 -> 1 More interesting math: http://mathworld.wolfram.com/

the following:

- if it is even, divide it by 2

- if it is uneven multiply it by 3 and add 1

Do this repeatedly and you'll always get to "1" The funny part is that there is no absolute proof for this rule, but

no-one has disproved it either. So far, each value taken as a start

value will end up being 1 in the end. Of course, the trick here is that

if you multiply an uneven number with 3 it will remain uneven. Add one,

it'll be even. So the final sequence will always be:

40-20-10-5-16-8-4-2-1 ... or does it? So, here's a try:

136 -> 68 -> 34 -> 17 -> 52 -> 26 -> 13 -> 40 -> 20 -> 10 -> 5 -> 16 ->

8 -> 4 -> 2 -> 1 More interesting math: http://mathworld.wolfram.com/