Genealogy: Two Ahnentafel number related calculation spreadsheets and how to write them

A spreadsheet which, given an Ahnentafel number from an offspring’s Ahnentafel list, will calculate which parent’s (FATHER or MOTHER) Ahnentafel list it maps to and which Ahnentafel number on this list it maps to.

How to write the sheet

Put the appropriate headings into cells A1, B1 and C1 and then put an Ahnentafel number from an offspring’s Ahnentafel list into cell A2. Into cell B2, put the formula =IF(A2-2^INT(LOG(A2,2))+1>2^(INT(LOG(A2,2))-1),”MOTHER”,”FATHER”) and into cell C2, put the formula =IF(A2-2^INT(LOG(A2,2))+1>2^(INT(LOG(A2,2))-1),A2-2^INT(LOG(A2,2)),A2-2^(INT(LOG(A2,2))-1))

A spreadsheet which, given a parent (FATHER or MOTHER) and an Ahnentafel number from that parent’s Ahnentafel list, will calculate the Ahnentafel number on their offspring’s Ahnentafel list mapped to.

How to write the sheet

Put the appropriate headings into cells A1, B1 and C1 and then put either FATHER or MOTHER into cell A2, an Ahnentafel number from that parent’s Ahnentafel list into cell B2, and into cell C2, put the formula =IF(A2=”FATHER”,B2+2^INT(LOG(B2,2)),B2+2^(INT(LOG(B2,2))+1))

Richard Purvey April 2024