-- this will take ~6h to run... need efficiency! function reversible(n) local revn = n:reverse() local str = tostring(n + revn) return not str:match("[02468]") end local sum = 0 for i = 1, 999999999 do if i % 10 ~= 0 and reversible(tostring(i)) then sum = sum + 1 end end print(sum)