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 only 1 interaction.
If there are 3 children, there can be 4 interactions.
If there are 4 children, there can be 9 interactions.

Which recursive equation represents the pattern?

an = an – 1 + 3n – 2
an = an – 1 + 2n – 3
an = an – 1 + (3n – 2)
an = an – 1 + (2n – 3)

Answer 1

i dont like the interaction numbers, they look weird

(x-1)^2?