Strictly speaking, of course, when Gene Roddenberry was first pitching Star Trek (TOS), while he had the Drake Equation in mind, he didn't have it with him and had to make up something on the fly.

I also understand that the equation was modified for The Big Bang Theory to extrapolate the odds of the show's protagnists in hooking up with the opposite sex.

A variation of which is now employed by my nephew, as he prepares for his freshman year at college. (Need I explain that his name is Drake?)