Consider the sequence 2, 6, 12, 20, 30

The sequences goes by 2.

The difference between the first two number is 4.

The difference between the second and third number is 6.

The difference between the third and fourth number is 8.

The difference between the fourth and fifth number is 10.

So therefore the sequence goes by 2.

hope this helps,if you have any questions please don't hold back to message me :)

(6,0) i hope it makes enough sense