The Nikon F mount was introduced in the summer of 1959 and has been the company’s primary lens mount ever since. This mount is still used in every Nikon SLR and DSLR to this day.
Nikon’s early lenses communicated aperture information to the body using a metal coupling fork, colloquially known as "bunny ears". Nowadays these lenses are labeled "Non-Ai" or "Pre-Ai", since they predate the Ai system. This system uses a small plastic tab on the aperture ring to communicate aperture information to the body. Even though most modern lenses communicate electronically, Nikon's professional DSLRs still retain this mechanical system, allowing vintage lenses to be used normally. Pre-AI lenses can cause mechanical damage to later model bodies unless they are modified to meet the AI specification.
The F mount is one of the most successful, long-running mounts of all time, and thus has an incredible variety of focal lengths and manufacturers. If you want a particular focal length, the Nikon F mount most likely has it!