Sequence: 4, 13, 28, 49
Now, differences between numbers = 13-4, 28-13, 49-18
= 9, 15, 21
We can see, difference is increasing by 6 at each step, so it would be 27 for next.
Next number = 49 + 27 = 76
In short, Your Answer would be 76
Hope this helps!