This is about the most efficient way to pack that number of circles. By looking at the bottom row of the 49, you can see that it’s slightly less wide than 7 diameters, because it has 5 circles at the very bottom (taking up 5 diameters of width), but two are slightly raised, which also means they’re slightly inward.
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https://en.m.wikipedia.org/wiki/Circle_packing
This is about the most efficient way to pack that number of circles. By looking at the bottom row of the 49, you can see that it’s slightly less wide than 7 diameters, because it has 5 circles at the very bottom (taking up 5 diameters of width), but two are slightly raised, which also means they’re slightly inward.