Erdős-primes: Difference between revisions
Added Lua version
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The 7875th Erdős prime is 999,721
</pre>
=={{header|Lua}}==
<syntaxhighlight lang="lua">function isPrime (x)
if x < 2 then return false end
if x < 4 then return true end
if x % 2 == 0 then return false end
for d = 3, math.sqrt(x), 2 do
if x % d == 0 then return false end
end
return true
end
function primes ()
local x, maxInt = 3, 2^53
local function yieldPrimes ()
coroutine.yield(2)
repeat
if isPrime(x) then coroutine.yield(x) end
x = x + 2
until x == maxInt
end
return coroutine.wrap(function() yieldPrimes() end)
end
function factorial (n)
local f = 1
for i = 2, n do
f = f * i
end
return f
end
function isErdos (p)
local k, factK = 1
repeat
factK = factorial(k)
if isPrime(p - factK) then return false end
k = k + 1
until factK >= p
return true
end
local nextPrime, count, prime = primes(), 0
while count < 7875 do
prime = nextPrime()
if isErdos(prime) then
if prime < 2500 then io.write(prime .. " ") end
count = count + 1
end
end
print("\n\nThe 7875th Erdos number is " .. prime)</syntaxhighlight>
{{out}}
<pre>2 101 211 367 409 419 461 557 673 709 769 937 967 1009 1201 1259 1709 1831 1889 2141 2221 2309 2351 2411 2437
The 7875th Erdos number is 999721</pre>
=={{header|Mathematica}}/{{header|Wolfram Language}}==
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