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#!/opt/local/bin/lua
--
-- See https://theweeklychallenge.org/blog/perl-weekly-challenge-147
--
--
-- Run as: lua ch-1.lua
--
function is_prime (p)
if p == 2 then
return true
end
if p % 2 == 0 then
return false
end
i = 3
while i * i <= p do
if p % i == 0 then
return false
end
i = i + 2
end
return true
end
todo = {2, 3, 5, 7}
for i, p in ipairs (todo) do
io . write (p, " ")
end
count = 20 - #todo
pow = 10
while #todo > 0 do
new_todo = {}
for d = 1, 9 do
for i, p in ipairs (todo) do
candidate = d * pow + p
if is_prime (candidate) then
io . write (candidate, " ")
new_todo [#new_todo + 1] = candidate
count = count - 1
if count <= 0 then
goto end_of_while
end
end
end
end
todo = new_todo
pow = pow * 10
end
::end_of_while::
io . write ("\n")
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