A number chain is created by continuously adding the square of the digits in a number to form a new number until it has been seen before.
For example,
44 32
13
10
1
1
85 89
145
42
20
4
16
37
58
89
Therefore any chain that arrives at 1 or 89 will become stuck in an endless loop. What is most amazing is that EVERY starting number will eventually arrive at 1 or 89.
How many starting numbers below ten million will arrive at 89?
These problems are part of Project Euler and are licensed under CC BY-NC-SA 2.0 UK