int LEDpins[] = {13, 12, 11};
int n = 0;

void setup() {
  pinMode( 2, INPUT_PULLUP);
  for( int i=0; i < 3; i++ ) {
    pinMode( LEDpins[i], OUTPUT);
  }
  digitalWrite( 13, LOW);
}

int pButton = -1;
void loop() {
  int b = digitalRead(2);
  if ( b != pButton ) {
    pButton = b;
    if (!b) {
      n = (n+1) % 8;
      digitalWrite( 13, n & B0001 ? HIGH : LOW );
      digitalWrite( 12, n & B0010 ? HIGH : LOW );
      digitalWrite( 11, n & B0100 ? HIGH : LOW );
    }
  }
  delay(10);
}