Question

A playground is being designed where children can interact with their friends in certain combinations.

If there is 1 child, there can be 0 interactions.
If there are 2 children, there can be 3 interactions.
If there are 3 children, there can be 9 interactions.
If there are 4 children, there can be 18 interactions.

Which recursive equation represents the pattern?

Answer 1

if we look at the first 4 values
0,3,9,18, ...
notice they are increasing by 3, 6, 9, ...