int i = 0;
int array[4] = {2, 3, 5, 7};
int  x = 0;
unsigned char k=0;

void setup() {
   Serial.begin(9600);
  Serial.println("Enter a value for K (0-99): ");
  while (!Serial.available()) {
    ;
  }
  k = Serial.parseInt();
}

void loop() {
  while (x <= 100) {
    bool Ans = false;
    for (i = 0; i < 4; i++) {
      if (x % array[i] == 0 && x / array[i] != 1 ) {
        Ans = true;
        break;
      }
    }
    if (!Ans && x != 1 && x <= k) {
      Serial.println(x);
    }
    x++;
  }
  delay(100);
}