7:47 AM
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In math, i.e. at math.stackexchange and mathoverflow, the blackboard bold symbols for: ℕ — Natural Numbers ℤ — Integers ℚ — Rational Numbers ℝ — Real Numbers ℂ — Complex Numbers are used very frequently. They can be generated by $\mathbb N$ etc. for example, but TeX macros like $\N$ for \$\m...