Permutations at most x duplicates in article

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Let's say we have 50 numbers (1 - 50). Each data set contains 5 numbers.

How many sets are there, where there are at most x duplicates between two sets. No duplicates within a set are allowed.

Example with less data; Let's say we have 10 numbers: 1,2,3,4,5,6,7,8,9,10 Let's say a set contains 4 numbers.

We want all sets with at most 2 duplicates between two sets.

  • 1,2,3,4
  • 1,2,5,6
  • 1,2,7,8
  • 1,2,9,10
  • 1,3,5,7
  • 1,3,6,8
  • 1,4,5,7
  • etc

I don't even know where to begin with the calculation.