How I calculated my F Stop according to my length to film plane distance

Описание: When photographing a small object I came up with a way to calculate the true F stop I was using, and I wanted to share with you how I did it.
Incidentally here are the series of F Stops as calculated from the largest aperture to the smallest...
F 1, F 1.4, F 2, F 2.83, F 4, F 5.66, F 8, F 11.31, F 16, F 22.61, F 32, F 45.21,
F 64, F 90.4, F 128, F 180.75, F 256, F 361.39, etc.
I simply multiplied 1.414 with one and continued from there to get these numbers. It is interesting to note that I embarked on these numbers because I saw a video of Edward Weston's grandson talking about the photograph "Pepper #30." He says that his grandfather came up with making his own F stops (because he was photographing so close that he could not obtain the depth of focus he wanted at F 64). And he wound up using F 240 and an exposure time of between 4 to 6 hours.
This didn't make sense to me an so I started calculating my own progression of F stops. It also didn't make sense that the exposure would be 4 to 6 hours long. I still don't understand how F 240 or an hours long exposure came about.