357

p357.lua

--Solves Project Euler problem 357.

function filltablesieve(lim, qf)
  local sievetable = {}
  for i = 1, lim do sievetable[i] = false end --use optimized tables
  for i = 1, lim do
    for j = i, lim / i, 1 do
      sievetable[j * i] = sievetable[j*i] or qf(i, j)
    end
  end
  return sievetable
end
function primetest(primetable) --closure uses primetable to test for primality
  return function(i, j)
    return primetable[i + j]
  end
end
primegenerators = filltablesieve(100000000, primetest(filltablesieve(200000000, function(i) return i > 1 end)))
sum = 0
for i = 1, 100000000 do
  if not primegenerators[i] then sum = sum + i end
end
print(sum)