Deceptive numbers: Difference between revisions

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=={{header|Lua}}==

Based on the second Wren sample, finds the numbers without needing large integers - see the talk page for more details.

<syntaxhighlight lang="lua">

do -- find deceptive numbers - repunits evenly divisible by composite numbers

-- see tha task talk page based on the second Wren sample

-- returns true if n is prime, false otherwise, uses trial division %

local function isPrime ( n )

if n < 3 then return n == 2

elseif n % 3 == 0 then return n == 3

elseif n % 2 == 0 then return false

else

local prime = true

local f, f2, toNext = 5, 25, 24

while f2 <= n and prime do

prime = n % f ~= 0

f = f + 2

f2 = toNext

toNext = toNext + 8

end

return prime

end

end

do -- task

local n, count = 47, 0

while count < 25 do

n = n + 2

if n % 3 ~= 0 and n % 5 ~= 0 and not isPrime( n ) then

local mp = 10

for p = 2, n - 1 do mp = ( mp * 10 ) % n end

if mp == 1 then

count = count + 1

io.write( string.format( " %5d", n ) )

if count % 10 == 0 then io.write( "\n" ) end

end

end

end

end

end

</syntaxhighlight>

{{out}}

<pre>

91 259 451 481 703 1729 2821 2981 3367 4141

4187 5461 6533 6541 6601 7471 7777 8149 8401 8911

10001 11111 12403 13981 14701