Pattern: 0, 1, 3, 6, 10, 15, __

Explain the pattern of these numbers.

21

Step-by-step explanation:

0 + 1 = 1

1 + 2 = 3

3 + 3 = 6

6 + 4 = 10

10 + 5 = 15

15 + 6 = 21

Each number is added to an increase of 1 - first add 1, then add 2, then add 3, etc

Not listed but next would be 21 + 7 = 28

so it would be 0, 1, 3, 6, 10, 15, 21, 28