What number is banned in China?

Excuse me, could you please elaborate on the context in which the question "What number is banned in China?" arises? Is it related to a specific cultural taboo, a government regulation, or perhaps a superstition? Without further context, it's difficult to give a precise answer, as the ban on a particular number could stem from various reasons. However, in general, if we're considering superstitions, the number four (4) is often considered unlucky in Chinese culture due to its pronunciation sounding similar to the word for "death" (si). But if it's a government regulation, I'd need more information to provide an accurate response. Could you please clarify the context of this question?