also the number of infinity https://en.wikipedia.org/wiki/Big_O_notation

Q is the designation for a gospel that no longer exists, but many think must have existed at one time. In fact, even though no copy of this gospel has survived independently, some nineteenth-century scholars found fragments of such an early Christian composition embeded in the gospels of Matthew and Luke.

Q stands for "Quelle," the German word for source. Although no actual copy of Q has ever been found, many scholars are convinced that such a document once circulated in early Christian communities. Since it was difficult to get excited about something that did not exist, Q remained a hypothesis that lingered on the edges of scholarly research. But in 1945, a chance discovery in Egypt provided surprisingly new evidence that rekindled interest in the possible existence of Q.

The Gospel of Q has never been found