Mathematics · Set Theory
An infinite binary word a is a string (a 1 a 2 a 3 ...), where each a n ∈ {0, 1}. Fix a word s = (s 1 s 2 s 3 ...), where s n = 1 if and only if n is prime. Let S = {a = (a 1 a 2 a 3 ...) | ∃m ∈ ℕ such that a n = s n , ∀n ≥ m}. What is the cardinality of S?
- 11
- 2Finite but more than 1
- 3Countably infinite✓
- 4Uncountable
Correct answer
Countably infinite
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