  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 (proband or progenitor) of the ahnentafel is listed as no. 1, the subject's father as no. 2 and the mother as no. 3, the paternal grandparents as no. 4 and no. 5 and the maternal grandparents as no. 6 and no. 7, and so on, back through the generations. apart from no. 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. 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 e-mails 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). the ahnentafel system of numeration is also known as: the eytzinger method, for michaÃ«l eytzinger, the austrian-born historian who first published the principles of the system in 1590;eytzinger, michael, thesaurus principum hac aetate in europa viventium, quo progenitores eorum... simul ac fratres et sonores inde ab origine reconduntur... usque ad annum..., cologne: g. kempensem, 1590 (1591). note: in commentaries, his surname may appear in variant forms, including: aitsingeri, aitsingero, aitsingerum, eyzingern. the sosa method, named for jerÃ³nimo (jerome) de sosa, the spanish genealogist who popularized the numbering system in his work noticia de la gran casa de los marqueses de villafranca in 1676;jouniaux, lÃ©o, gÃ©nÃ©alogie : pratique, mÃ©thode, recherche, quercy: seuil, 2006, pp. 44â45. and the sosaâstradonitz met
Genealogy