Why do this
is so simple and yet it requires a good
detective-type mind to explore it. The answer can be expressed in
very many different ways.
You might lead up to this by using simple examples, focusing
on encouraging children to explain how they know what the next
number is each time.
Tell me about how you got your answer.
How could you get from this number to the next
You could create some similiar examples, or encourage pupils
to make up their own. It would be interesting to give only two
numbers as a start so that there are many possibilities for
extending the sequence. Encourage children to find as many
different ways of continuing it as they can.
Use of calculators may help.