main.dart

void main() {
 int n = 4;
  
 int besideSq = 2 * beside(n);
 int middleSq = middle(n);
  
 int totalSquares = besideSq + middleSq;
  
 print(totalSquares);
  
}

int beside(int n){ //numbers of squares from each side
  int squares = 0;
  for(int i=1; i<(2 *(n-1)); i+=2){
    squares += i;
  }
  return squares;
}

int middle(int n){ //number of squares from middle row
  return 1 + 2 * (n-1);
}