//Declaring "i" to be used in for-loop
int i;

//Naming pins to something more clear
int pin0 = 2; 
int pin1 = 0;
int pin2 = 4;
int pin3 = 16;

//Creating array with pins in alternating order
int ledLoop[] {pin0, pin1, pin2, pin3, pin2, pin1};

void setup() {
  //Setting pins to output mode
  pinMode(pin0, OUTPUT);
  pinMode(pin1, OUTPUT);
  pinMode(pin2, OUTPUT);
  pinMode(pin3, OUTPUT);

  //Turning on pins to check if they work
  digitalWrite(pin0, HIGH);
  digitalWrite(pin1, HIGH);
  digitalWrite(pin2, HIGH);
  digitalWrite(pin3, HIGH);

  delay(100);

  //Turning off pins
  digitalWrite(pin0, LOW);
  digitalWrite(pin1, LOW);
  digitalWrite(pin2, LOW);
  digitalWrite(pin3, LOW);

  delay(500);
}

void loop() {
  //Initiating the function
   ledActivate();
}

void ledActivate() {
  //Creating the function that alternates the leds in correct order, turning them on and off again
  for(i = 0; i < 6; i++) {
    digitalWrite(ledLoop[i], HIGH);
    delay(100);
    digitalWrite(ledLoop[i], LOW);
    delay(100);
  }
}