void setup() {
  pinMode(13, OUTPUT);  
  pinMode(6, OUTPUT);  
}

void loop() {
  for (int i = 0; i <= 9; i++) {
    
    bool lsb = (i & 0x01);     
    bool secondBit = (i & 0x02) >> 1;  

    if (lsb == 1) {
      digitalWrite(13, HIGH);  
    } else {
      digitalWrite(13, LOW);   
    }
    if (secondBit == 1) {
      digitalWrite(6, HIGH);  
    } else {
      digitalWrite(6, LOW);   
    }
    delay(1000);
  }
}