int ledPin[] = {13, 12, 11, 10};
int ledDelay[4]={8000, 4000, 2000, 1000};

int currTime;
int T1 ;
int T2 ;
int T3 ;
int T4 ;

int led0 = HIGH;
int led1 = HIGH;
int led2 = HIGH;
int led3 = HIGH;

void setup()
{
  for (int i = 0; i < 4; i++)
  {
    pinMode(ledPin[i], OUTPUT);
  }
}


void loop()
{
  currTime = millis();

  if (currTime - T1 > ledDelay[0])
  {
    digitalWrite(ledPin[0], led0);
    T1 = currTime;
    led0 = !led0;
  }

  if (currTime - T2 > ledDelay[1])
  {
    digitalWrite(ledPin[1], led1);
    T2 = currTime;
    led1 = !led1;
  }

  if (currTime - T3 > ledDelay[2])
  {
    digitalWrite(ledPin[2], led2);
    T3 = currTime;
    led2 = !led2;
  }

  if (currTime - T4 > ledDelay[3])
  {
    digitalWrite(ledPin[3], led3);
    T4 = currTime;
    led3 = !led3;
  }
}