Alphanumeric Generation & Validation for IDs

I need a script or program that generates 16-character alphanumeric codes and validates them, ensuring they meet specific criteria. These codes will be used as identification codes, and it's crucial that each code is unique.

Key Requirements:
- Generate 16-character alphanumeric codes
- Ensure each code consists of at least one letter and one number
- Check if the code meets a specific length requirement
- Verify the code does not contain any special characters
- Ensure each generated code is unique

Ideal Skills:
- Proficiency in scripting or programming
- Experience in generating and validating alphanumeric codes
- Understanding of data uniqueness and validation
- Attention to detail to ensure code quality
- Knowledge of security and identification code best practices