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- #!/usr/bin/ruby
- # Smallest k such that 2^(2^n) - 2^k - 1 is prime, or 0 if no such k exists.
- # https://oeis.org/A232565
- # Known terms:
- # 0, 1, 2, 4, 2, 8, 18, 76, 32, 151, 692, 592, 154, 580, 27365
- # Found:
- # a(16) = 11267
- # a(17) > 12
- var n = 17
- var v = (2**(2**n) - 1)
- var from = 13
- for k in (from .. 1e9) {
- say "Testing: #{k}"
- if (v - (1<<k) -> is_prob_prime) {
- die "Found: #{k}\n"
- }
- }
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