This is very similar to the 2, 0, 1, 8 problem. Just try to make all numbers 1-30 using the digits 2, 0, 1, 9.
Rules:
- Use all four digits exactly once
- Allowed operations: +, -, x, ÷, ! (factorial), exponentiation, square root
- Parentheses and concatenation are allowed (e.g. $20 + (1 * 9)$)
- Squaring uses the digit 2 so expressions using multiple twos, like 22 or $12+92$, are not allowed
- Keep the order "2 0 1 9" in all expressions
- The modulus operator is not allowed
- Rounding is not allowed (e.g. $201/9=22$)