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I have come across 6-element rings, 5-element rings, but very rarely 3,4, or 7,8, etc. -element rings. I am not sure of the reason for the rarity of other rings than 5 or 6. Is it just what I have encountered so far do not include non-5/6 rings a whole lot, or is it because of some reasons that there just are not that many non-5/6 rings around?
Edit: The rings I am referring to include both same-element (e.g. benzene, octasulfur, etc.) and different-element (e.g. glucose, fructose, etc.) ones.