Aplayground 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 5 interactions.
if there are 4 children, there can be 14 interactions.

which recursive equation represents the pattern?

an = an - 1 + 2(n - 1)

an = an - 1 + (n - 1) 2

an = an - 1 + 2(n - 1)

an = an - 1 + (2n - 1)