float timer1 = 78.9856655;  // set timer.

void setup() {

  // use a for loop to initialize each pin as an output:

  for (int ledPin = 2; ledPin < 13; ledPin++) {

    pinMode(ledPin, OUTPUT); // initialize ledPin as an output:
  }
}
void loop() {

  // loop run from the ledPin 6 to ledPin 13:

  for (int ledPin = 6; ledPin < 13; ledPin++) {

    digitalWrite(ledPin, HIGH);// set pin on:
    delay(timer1); // call the timer1: 
    digitalWrite(ledPin, LOW);// set pin off:
  }

  // loop run from the ledPin 13 to ledPin 6:

  for (int ledPin = 13; ledPin >= 6; ledPin--) {
    
    digitalWrite(ledPin, HIGH);// set pin on:
    delay(timer1); // call the timer1: 
    digitalWrite(ledPin, LOW);// set pin off:
  }
}