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Posted By Peter Bentley
Here's a recent email exchange about the history of numbers, relating to the descriptions in The Book of Numbers

One month ago I finished reading your fascinating book "the Book of Numbers". From that moment on your question: Where are all the girls? keeps lingering through my mind. I wonder how many girls did react on this question.

I'm glad you enjoyed the book. So far you are the first to tell me about your reaction to that specific question. Let's hope a few more girls do become more interested in the subject!

You wrote about Euler, Pierre de Fermat and Descartes concerning amicable numbers.

I just happened to read the following text on the internet: Arabic mathematics : forgotten brilliance?

…Continuing the story of amicable numbers, from which we have taken a diversion, it is worth noting that they play al large role in Arabic mathematics. Al-Farisi (born 1260) gave a new proof of Thabit ibn Qurra’s theorem, introducing important new ideas concerning factorisation and combinatorial methods. He also gave the pair of amicable numbers 17296, 18416 which have been attributed to Euler, but we know that these were known earlier than al-Farisi, perhaps even by Thabit ibn Qurra himself. Although outside our time range for Arabic mathematics in this article, it is worth noting that in the 17th century the Arabic mathematician Mohammed Baqir Yazdi gave the pair of amicable number 9,363,584 and 9,437,056 still many years before Euler’s contribution……

Perhaps it is of interest for you.

yes, when describing amicable numbers I wrote "(although some claim that they may also have been known before this)". I was referring to this text you found. There is some debate over the issue, but it is probably true that the Arabs had found many amicable numbers, which were then forgotten for several hundred years and rediscovered by the likes of Descartes and Euler. The University of St Andrews is an excellent source of information on this topic - I used their help when writing the Book of Numbers.

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