public static void eratoImproved(long max){

        long start = System.currentTimeMillis();

        List<Long> invalidated = new ArrayList<>(); // where invalidated numbers will be stored.

        // prepare
        double maxFac = Math.sqrt(max);
        for(long f = 2; f <= maxFac; f++){
            boolean isNew = true;
            for(long l : invalidated){
                if(f % l == 0){
                    isNew = false;
                }
            }
            if(isNew) {
                invalidated.add(Math.round(f + 0.0));
            }
            f++;
        }

        ArrayList<Long> primes = new ArrayList<>();


        for(long prime : invalidated){
            primes.add(prime);
        }

        for(long i = 3; i <= max; i += 2){
            boolean v = true;
            for(long s : invalidated){
                if(i % s == 0){
                    v = false;
                    break;
                }
            }

            if(v){
                primes.add(i);
                if(primes.size() >= 150){
                    String s = Math.round(((i + 0.0)/max)*100) + "%: ";
                    for(long l : primes){
                        s += l + "/";
                    }
                    System.out.println(s);
                    primes.clear();
                }

            }
            i += 2;
        }
        System.out.println("Completed search!");
        String s = "Remaining primes: ";
        for(long l : primes){
            s += l + "/";
        }
        System.out.println(s);
        primes.clear();

        System.out.println("Conducted search in " + (System.currentTimeMillis() - start)/1000 + " seconds.");
    }