H.M.M gracel Series

It seems like you're referring to a specific series or concept called "H.M.M. gracel series," but there isn't a recognized series by that name in widely known mathematical literature or popular topics. Could you please provide a little more context or clarify what you mean by "H.M.M. gracel series"? Are you looking for information on a mathematical series, a statistical method, a specific application, or something else? This additional detail will help me assist you more effectively.