even simpler

emily2.pde

int pinCount = 4;                                // the number of pins
int thisPin;

void setup() {                                   // set up the app
  for (int thisPin = 1; thisPin <= pinCount ; thisPin++) {
    setupPin(thisPin);
  }
}
 
void loop()          
{
  for (int thisPin = 1; thisPin <= pinCount; thisPin++) {
    turnOnPin(thisPin);
    delay(300);
    turnOffPin(thisPin);
  }
}

void setupPin(int i) {
  switch(i) {
    case 1:
      pinMode(A5, OUTPUT);
      break;
    case 2:
      pinMode(A2, OUTPUT);
      break;
    case 3:
      pinMode(10, OUTPUT);
      break;
    case 4:
      pinMode(5, OUTPUT);
      break;
    }
}

void turnOnPin(int i) {
  switch(i) {
    case 1:
      digitalWrite(5, HIGH);
      break;
    case 2:
      digitalWrite(10, HIGH);
      break;
    case 3:
      digitalWrite(A2, HIGH);
      break;
    case 4:
      digitalWrite(A5, HIGH);
      break;
    }
}

void turnOffPin(int i) {
  switch(i) {
    case 1:
      digitalWrite(5, LOW);
      break;
    case 2:
      digitalWrite(10, LOW);
      break;
    case 3:
      digitalWrite(A2, LOW);
      break;
    case 4:
      digitalWrite(A5, LOW);
      break;
    }
}