If your lamp socket threads are larger than the normal size, it's for a "mogul" base bulb. You can search online or a good hardware store should have them. Typically, mogul bulbs are large, bright and cost more. They are available in regular tungsten, LED and specialty gas filled that require transformer wiring.

Another option is to use a "mogul to medium" adapter so you can use any normal household thread bulb.
https://www.acehardware.com/departm...nd-accessories/sockets-and-holders/30859

Jim "Oldgas" Potts
Your host and moderator