dddd

Here in the foothills, we have to be able to handle occasional pitches up near 20%, and to be able to recover to finish the return ride.

So for me, I found that 42/28t = 39/26t = 36/24t.

This ratio gets the job done, and I can even squeeze a full range of gears into 7 sequential ratios using just a 5-speed freewheel (13-24t) with a 36-52t chainset.
When I shift to (or from) the big chainring, I simultaneously shift to (or from) the largest 24t cog, breaking the big chainring gearing gap down to be similar to just one shift in back. This results in a total of seven sequential ratios.

Used on a variety of bikes, some heavy, I hope to make it through my 50's with this lowest gear.
It helps that I am a lightweight who rides several times per week in this hilly area, and that our weather mostly allows this, year-round.