ahnentafel

thumb|right|300px|The first ahnentafel, published by Michaël Eytzinger in Thesaurus principum hac aetate in Europa viventium Cologne: 1590, pp. 146–147, in which Eytzinger first illustrates his new functional theory of numeration of ancestors; this schema showing Henry III of France as n° 1, de cujus, with his ancestors in five generations. The remainder of the volume shows 34 additional schemas for rulers and princes of Europe using his new method. thumb|Seize quartiers [[coat of arms display document (1786)]] 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 of ascent. The subject (or proband) of the ahnentafel is listed as , the subject's father as and the mother as , the paternal grandparents as and and the maternal grandparents as and , and so on, back through the generations. Apart from , 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 definition of numeration, one can derive some basic information about individuals who are listed without additional research.

This construct displays a person's genealogy compactly, without the need for a diagram such as a family tree. It is particularly useful in situations where one may be restricted to presenting a genealogy in plain text, for example, in emails or newsgroup articles. In effect, an ahnentafel is a method for storing a binary tree in an array by listing the nodes (individuals) in level-order (in generation order).