What is the number rule for 18250, 18500, 19000, 20000

The number rule for this sequence is that each time the number goes up, it does so by whatever the previous amount added was, multiplied by two. So far we can see the sequence is + 50, + 25-, + 500, + 1000, so we assume that next it will be + 2000 and the next number in the sequence will therefore be 22,000