const int SIZE = 5;

int arrayOfLEDpins[SIZE] = {1, 3, 5, 7, 9};

int Twait = 100;

void setup() {
  for (int i = 0; i <= SIZE-1; i++)
  {
    pinMode(arrayOfLEDpins[i], OUTPUT);
  }

}

void blinkrtl() {
  for (int i = 0; i <= SIZE-1; i++)
  {
    digitalWrite(arrayOfLEDpins[i], HIGH);
    delay(Twait / 4);
    digitalWrite(arrayOfLEDpins[i], LOW);
    delay(Twait);
  }
}

void blinkltr() {
  for (int i = 3; i>= 1; i--){
    digitalWrite(arrayOfLEDpins[i], HIGH);
    delay(Twait / 4);
    digitalWrite(arrayOfLEDpins[i], LOW);
    delay(Twait);
  }
}

void loop() {
  blinkrtl();
  blinkltr();
}