Yes. It's ok to bring a blank notepad and pen into an interview. I rarely see candidates do this, but have never had a problem when one did. I noticed they did so to write a word or two to remind themselves of the focus of the question and we had no issue with them doing so.
However, if we saw that you had notes on that notepad, you could expect to be asked to close the notepad. We're conscious of being fair to all candidates and wouldn't want one having notes when others in that competition hadn't.
Tina's Blog - Interviewer Insights
My interview tips are based on my years of interviewing experience and my years of interview coaching.