experimental-projects/oeis-research/Farideh Firoozbakht/Concatenation of first n primes joined with 0 is prime/prog.sf

#!/usr/bin/ruby

# Numbers n such that concatenation of first n primes, separated by zeros, is prime.
# https://oeis.org/A082549

# Known terms:
#   1, 9, 15, 25, 59, 444

# Next term >= 5686

# Heuristically, the next term should be close to 8000.

for n in (5686..7000) {
    var t = primes(prime(n)).join('0').to_i
    say "Testing: #{n} -- length #{t.len}"
    if (t.is_prob_prime) {
        die "Found: #{n}"
    }
}