I'm not sure but it could be numbers written in base 5. The 5 units = 5^1 so the last digit doesn't ever exceed 4.

I.e 5^3 5^2 5^1 5^0 as column headings instead of base 10 (usually used) thousands hundreds tens units etc 10^3 10^2 10^1 10^0

1111 means (1)5^3 + (1)5^2 + (1)5^1 + (1)5^0 or 125 + 25 + 5 + 1 = 156 in base 10

1112 means (1)5^3 + (1)5^2 + (1)5^1 + (2)5^0 or 125 + 25 + 5 + 2 = 157 in base 10

1120 means (1)5^3 + (1)5^2 + (2)5^1 + (0)5^0 or 125 + 25 + 10 + 0 = 160 in base 10 (this was not mention in your list though)

Hope that helps.