// define the pins for the LEDs
int ledPins[] = {22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53};

// set the number of LEDs
int numLeds = sizeof(ledPins) / sizeof(int);

// set the delay time between LED updates
int delayTime = 50;

// set the current LED index
int currentLed = 0;

// set the current LED direction
int direction = 1;

void setup() {
  // initialize all LED pins as outputs
  for (int i = 0; i < numLeds; i++) {
    pinMode(ledPins[i], OUTPUT);
  }
}

void loop() {
  // turn off the current LED
  digitalWrite(ledPins[currentLed], LOW);

  // increment the current LED index
  currentLed += direction;

  // check if we've reached the end of the LED array
  if (currentLed == numLeds - 1 || currentLed == 0) {
    direction = -direction;
  }

  // turn on the new current LED
  digitalWrite(ledPins[currentLed], HIGH);

  // delay before updating the LEDs again
  delay(delayTime);
}