int myarray[13]={1,2,3,4,5,6,7,8,9,10,11,12,13};
void setup()
{
for(int i=0;i<=12;i++)// put your setup code here, to run once:
{
  pinMode(myarray[i], OUTPUT);
}
}

void loop() {
 for(int i = 0;i<=12;i++) // put your main code here, to run repeatedly:
{digitalWrite(myarray[i],1);
delay(200);
}

for(int j=12;j>=0;j--)
{digitalWrite(myarray[j],0);
delay(200);
}
}