int LedPins [] = {13,12,11,10,9,8,7,6};
int tempo = 500;


void setup() 
{
  for (int i = 0; i < 8; i++)
  {
    pinMode(LedPins[i], OUTPUT);
  }
  randomSeed(millis());    //Initialize random number generator
}

void loop() 
{
  // Turn on by choice (select from array)
  digitalWrite(LedPins[0], HIGH);
  delay(tempo);
  digitalWrite(LedPins[0], LOW);
  delay(tempo);
  digitalWrite(LedPins[2], HIGH);
  delay(tempo);
  digitalWrite(LedPins[2], LOW);
  delay(tempo);
  digitalWrite(LedPins[4], HIGH);
  delay(tempo);
  digitalWrite(LedPins[4], LOW);
  delay(tempo);
  digitalWrite(LedPins[6], HIGH);
  delay(tempo);
  digitalWrite(LedPins[6], LOW);
  delay(tempo);

  // Turn on simple sequence
  for (int i = 0; i < 8; i++)
  {
    digitalWrite(LedPins[i], HIGH);
    delay(tempo);
  }

  // Reverse
   for (int i = 7; i > -1; i--)
  {
    digitalWrite(LedPins[i], LOW);
    delay(tempo);
  }
}