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- #!/usr/bin/ruby
- # Numbers n such that 2^n + 3^n is a semiprime.
- # https://oeis.org/A050244
- # a(34) > 23194.
- for k in (23194..1e6) {
- say "Testing: #{k}"
- if (is_semiprime(3**k + 2**k)) {
- die "Found: #{k}"
- }
- }
- # Numbers m such that 4^m - m is a semiprime.
- # https://oeis.org/A252657
- # Next term >= 483 -- http://factordb.com/index.php?id=1100000000251223208
- # Numbers m such that 10^m - m is a semiprime.
- # https://oeis.org/A252663
- # 107, 117, 143, 149, 177,
- # Numbers m such that m*10^m + 1 is a semiprime.
- # https://oeis.org/A216378
- # 111, 117, 123, 181, 184, 187,
- # Numbers k such that 1 + (product of first k primes) is a semiprime.
- # https://oeis.org/A085725
- # 76,
- # Numbers n such that 3^n-2 is a semiprime.
- # https://oeis.org/A080892
- # Next term >= 658 -- http://factordb.com/index.php?id=1000000000018245962
- # Numbers n such that Pell(n) is a semiprime.
- # https://oeis.org/A250292
- # Next term >= 709 -- http://factordb.com/index.php?id=1100000000707746051
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