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A 13th-Century Enumeration Algorithm, Ignored for 700 Years

This is the first article in a series about a discovery I made while researching Tserouf in the writings of the Kabbalist Abraham Aboulafia (1240 – after 1291). Tserouf is the Kabbalistic art of permuting the letters β€” and, in plain mathematical terms, it is the enumeration of all the permutations of an n -letter word.

In Or ha-Sekhel (β€œThe Light of the Intellect”), Aboulafia prescribes a systematic method for enumerating all the possible arrangements of an n -letter word. The method is conceived inside a frame of spiritual practice β€” and yet it carries a mathematical structure of remarkable rigour.

For a three-letter word, Aboulafia gives the Tserouf β€” the ordering of all six permutations β€” explicitly:

The words fall into three groups, by their first letter:

Aboulafia explicitly mentions two rules for the Tserouf of 3 letters:

Rule 1 β€” the mirror. The whole sequence must end on the reverse of where it began . Aboulafia says it plainly: β€œthe last utterance is the reverse of the first.” The first word is abc ; the last must be cba , its end-to-end reversal.