Epic Software Developer interview questions

One of the coding questions (paraphrasing) : a company wants you to write a function that will output all possible phone numbers of a certain length. They want to reduce confusion, and eliminate all phone numbers with duplicate digits next to each other (for example 0232 is acceptable, but 0223 is not.) The company also wants the option to possibly eliminate up to three numbers from the phone numbers as well. Another rule is that the phone numbers that contain any 4 must start with a 4 as well.