int pins[9] = {5,6,7,8,9,10,11,12,13,}; // 9 LEDs on pins ranging from 5 to 13
int time = 20;  // Time delay

void setup() {
  // put your setup code here, to run once:
for (int i = 0; i < 9; i++)  // The 9 LEDs ranging from 0 to 8 incrementally
{
pinMode(pins[i], OUTPUT);  // Assigned pin 5 to 13 as incremented output 
}
for (int i = 9; i > 0; i--)  // The 9 LEDs ranging from 8 to 0 decrementally
{
pinMode(pins[i], OUTPUT);  // Assigned pin 13 to 5 as decremented output
}
}

void loop() {
  // put your main code here, to run repeatedly:
for (int i = 0; i < 9; i++)  // For the LEDs to come on incrementally
{
digitalWrite(pins[i], HIGH);  // To make the 9 LEDS on 
delay(time);
digitalWrite(pins[i], LOW);  // To make the 9 LEDS off
delay(time);                 // Time delay
}
for (int i = 9; i > 0; i--)  //  For the LEDs to come on decrementally
{ 
digitalWrite(pins[i], HIGH);  //  To make the 9 LEDS on 
delay(time);                  //  Time delay
digitalWrite(pins[i], LOW);  //  To make the 9 LEDS off
delay(time);                 //  Time delay
}
}