int pins7[] = {2, 3, 4, 5, 6, 7, 8}; 

byte digits[10][7] = {
  {1,1,1,1,1,1,0}, 
  {0,1,1,0,0,0,0}, 
  {1,1,0,1,1,0,1}, 
  {1,1,1,1,0,0,1},
  {0,1,1,0,0,1,1}, 
  {1,0,1,1,0,1,1}, 
  {1,0,1,1,1,1,1}, 
  {1,1,1,0,0,0,0}, 
  {1,1,1,1,1,1,1}, 
  {1,1,1,1,0,1,1}  
};

int num = 0;
bool forward = true;

void setup() {
  for (int i = 0; i < 7; i++) {
    pinMode(pins7[i], OUTPUT);
  }
}

void loop() {
  
  for (int i = 0; i < 7; i++) {
    digitalWrite(pins7[i], digits[num][i]);
  }

  delay(1000);

  // 
  if (forward) {
    num++;
    if (num == 9) {
      forward = false;
    }
  } else {
    num--;
    if (num == 0) {
      forward = true;
    }
  }
}