#define MAXLED 8
int led[MAXLED] = {2,3,4,5,6,7,8,9};
void setup() {
  for (int i=0; i<MAXLED; i++)
  pinMode(led[i], OUTPUT);
}

void loop() {
for (int i=0; i<MAXLED; i++)
{
  prender(led[i], 50);
  apagar(led[i], 100);
}

for (int i=6; i>0; i--)
{
  prender(led[i], 50);
  apagar(led[i], 50);
}

}
void prender(int l,int t) {
digitalWrite(l, HIGH);
delay(t);
}
void apagar(int l,int t) {
  digitalWrite(l, LOW);
  delay(t);
  }