Hey I need some help with this math problem.

Find a formula for the nth term of the sequence

1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, ...

I can see the pattern, but I'm not sure how to go about finding a formula for this sequence. Hoping someone can guide me through this problem so I can understand it better thanks.