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#!/usr/bin/env lua
local function is_prime(n)
assert(type(n) == 'number', 'n must be a number!')
local i = 5
if n == 2 or n == 3 then return true end
if n <= 1 or n % 2 == 0 or n % 3 == 0 then return false end
while i * i <= n do
if n % i == 0 or n % (i+2) == 0 then return false end
i = i + 6
end
return true
end
local function prime_count(n)
assert(type(n) == 'number', 'n must be a number!')
local count = 0
for i=1,n-1 do
if is_prime(i) then count = count + 1 end
end
return count
end
print(prime_count(10))
print(prime_count(15))
print(prime_count(1))
print(prime_count(25))
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