Maja (Eastwood Primary School) noticed that:The pattern is, the colour of the border is the colour of the centre on the next square underneath and the square gets longer by $1$ line.
Maja is right, and because the square gets wider by $1$ unit each time, it also has to get taller by $1$ line so an extra rod is added to the centre each time. Continuing the pattern then, the next square will have $5$ yellow rods in the centre, surrounded by green rods. After that we will need $6$ green rods in the centre, surrounded by black rods. And so on.