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- #!/usr/bin/ruby
- # An interesting recursive function, involving the gcd() function for generating prime numbers.
- # If R(n) = 2*n + 2, then n+1 is prime. (conjectured?)
- func R((1)) { 7 }
- func R(n) is cached {
- R(n-1) + gcd(R(n-1), n)
- }
- each(1..10000, { |n|
- if (R(n) == (2*n + 2)) {
- say n+1
- }
- })
- __END__
- [5, 11, 23, 47, 101, 233, 467, 941, 1889, 3779, 7559]
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