Repunit primes: Difference between revisions

=={{header|Ruby}}==

Ruby's standard lib 'Prime' is boring slow for this. GMP to the rescue. GMP bindings is a gem, not in std lib.

<syntaxhighlight lang="ruby">require 'prime'

require 'gmp'

(2..16).each do |base|

res = Prime.each(1000).select {|n| GMP::Z(("1" * n).to_i(base)).probab_prime? > 0}

puts "Base #{base}: #{res.join(" ")}"

end

</syntaxhighlight>

{{out}}

<pre>Base 2: 2 3 5 7 13 17 19 31 61 89 107 127 521 607

Base 3: 3 7 13 71 103 541

Base 4: 2

Base 5: 3 7 11 13 47 127 149 181 619 929

Base 6: 2 3 7 29 71 127 271 509

Base 7: 5 13 131 149

Base 8: 3

Base 9:

Base 10: 2 19 23 317

Base 11: 17 19 73 139 907

Base 12: 2 3 5 19 97 109 317 353 701

Base 13: 5 7 137 283 883 991

Base 14: 3 7 19 31 41

Base 15: 3 43 73 487

Base 16: 2

</pre>