We copied the NASA data into an Excel spreadsheet, removed some of the nearly invisibe penumbral eclipses, and added a column showing the number of days from one eclipse to the next. The difference is always either 6 or sometimes 5 lunar months. We printed this bar graph, with bars in red, on paper. One, two, or three eclipses in a group are penumbral , meaning only the lighter part of earth's shadow touches the moon.
Penumbral eclipses are difficult or impossible to notice from earth.
In the table, the type is N, and PSD is zero. In the table, type is P and PSD is greater than zero. A group concludes with one or two partial eclipses. We would like to know if the groups form a longer pattern which repeats. Thus the pattern of the first group is repeated by the sixth group.