The differences are: 13-11=2, 20-13=7, 48-20=28, 111-48=63. These are 1×2, 2+5, 4×7, 9×7. Alternatively, differences of differences: 5, 21, 35, which increase by 16, 14. This is an inconsistent pattern. However, if we consider 2, 7, 28, 63 as following ×3.5, ×4, ×2.25, the next could be 111 + 126 = 237.