Embedded subsets

Task number: 3446

Determine the number:

  • Variant

    Of ordered pairs \((A, B)\), where \(A \subseteq B \subseteq \{1, 2, …, n\}\).

  • Variant

    Of ordered quadruples \((A, B, C, D)\), where \(A \subseteq B \subseteq D \subseteq \{1, 2, …, n\}\) and also \(A \subseteq C \subseteq D\).

Difficulty level: Easy task (using definitions and simple reasoning)
Proving or derivation task
Cs translation
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