Pairing 1 to 22 with differences of 1 or 11
Question
In how many ways can the set be split into two-element blocks so that in every block the two numbers differ by exactly or exactly ?
Short answer
. Write – above – in a grid: differences of are vertical neighbours and differences of are horizontal neighbours, plus one extra link between and . Domino tilings of a strip follow the Fibonacci recursion, giving for . Pairing forces everything else, adding more way.
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Open the worked solutionLessons behind this question
- Counting and Combinatorics
- Sample Spaces, Events, and the Probability Axioms
- Conditional Probability, Total Probability, and Bayes' Rule
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