docs: private static boolean isSequence(String asg, int dN) {
      int length = asg.length();
      if (length - dN < 3 || asg.charAt(dN + 1) != 'v') {
        return false;
      }
      for (int i = dN + 2; i < length; ++i) {
        if (!Character.isDigit(asg.charAt(i))) {
          return false;
        }
      }
      return true;
    }