Can the ratio of $q$-smooth numbers ever approach one? Asked more rigorously, can we ever have $$1\in \overline{\{a/b\; :\; a,b \;\text{ are } q\text{-smooth}\}}=\overline{\{\prod_{p_i\le q}p_i^{\alpha_i}\; :\; (a_1, \dots, a_{\pi(q)})\in\mathbb{Z}^{\pi(q)}\}}\;?$$ If $q=2$, the answer is obviously no because $$1\not\in \overline{\{2^{\alpha}\; :\; \alpha\in\mathbb{Z}\}}=\{0\}\cup \{2^{\alpha}\; :\; \alpha\in\mathbb{Z}\}$$ however beyond this the problem is not easy. The reason I would like to know this is because this would imply that $$G(q)=\inf \{a/b\; :\; a>b,\; a,b \; q\text{-smooth}\}>1.$$ I suspect that we may be able to say even further that $$\overline{\{\prod_{p_i\le q}p_i^{\alpha_i}\; :\; (a_1, \dots, a_{\pi(q)})\in\mathbb{Z}^{\pi(q)}\}}=\{0\}\cup \{\prod_{p_i\le q}p_i^{\alpha_i}\; :\; (a_1, \dots, a_{\pi(q)})\in\mathbb{Z}^{\pi(q)}\}$$ which would clearly imply the result.
2026-05-14 12:18:11.1778761091
Can ratio of smooth numbers approach 1?
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Yes, if $q\ge 3$.
This is because $\log_2(3)$ is irrational, so the fractional parts of $\log_2(3^n)$ lie densely in $[0,1)$. In particular they can become arbitrarily small.