int i; // counter variable 
int j; // pgm outputs codes 00000  to 00111 in portd 2-4 bits

void setup(){
 DDRD = DDRD | B00011100;    // set direction bits for pins 2 to 4, leave 0 and 1 untouched
 //(xx | 00 = xx)  same as pinMode(pin, OUTPUT) for pins 2 to 4
 Serial.begin(9600); 
} 

void loop(){ 
  for (i=7; i>0; i--)
  {                               // 3 bits manipulated 0 to 7
    PORTD = PORTD & B11100011;    // clear out bits 2 -4, leave pins 0 and 1 untouched (xx & 11 = xx)
    j = (i << 2);                 // shift variable up to pins 2 - 7 - to avoid pins 0 and 1
    PORTD = PORTD | j;            // combine the port information with the new information for LED pins 
    Serial.print("Counter variable i="); // debug to show masking 
    Serial.println(i);
    Serial.print("PORTD in BINary=");   // debug to show masking 
    Serial.println(PORTD, BIN);   // debug to show masking 
    delay(1000); 
  }
}