From Historical Hastings Wiki

An ahnentafel (German for "ancestor table") or ahnenreihe ("ancestor series") is a genealogical numbering system for listing a person's direct ancestors in a fixed sequence. The subject (proband) of the ahnentafel is listed as #1, the subject's father as #2 and the mother as #3, the paternal grandparents as #4 and #5 and the maternal grandparents as #6 and #7, and so on, back through the generations. Apart from #1, who can be male or female, all even-numbered persons are male, and all odd-numbered persons are female. In this schema, the number of any person's father is double the person's number, and a person's mother is double the person's number plus one. Using this knowledge of numeration, one can derive some basic information about individuals who are listed without additional research. Many of the genealogical constructs used within this wiki use templates and data structures from FamilyPedia.