I did a job application once where as part of the application you had to solve a simple math problem that was displayed at a specific URL[1]. The catch was that

I did a job application once where as part of the application you had to solve a simple math problem that was displayed at a specific URL[1]. The catch was that the math problem was different every time and expired in half a second, so the only way to do it was to script it. I guess its a time-based proof of work kind of thing. [1] IIRC, the URL would give you a simple arithmetic formula to solve and you would hit another URL with the result, something like /foo/<result> and it would give you a code. You then included the code in the application.