from Hacker News

Hardy, Ramanujan and Taxi No. 1729

by johncarlosbaez on 1/30/22, 8:36 PM with 21 comments

• by pdevr on 1/31/22, 6:41 AM

  >>I remember once going to see him when he was lying ill at Putney. I had ridden in taxi-cab No. 1729, and remarked that the number seemed to be rather a dull one, and that I hoped it was not an unfavourable omen. “No,” he replied, “it is a very interesting number; it is the smallest number expressible as the sum of two cubes in two different ways.”

  The quote above is from G. H. Hardy himself, from the book "Ramanujan: Twelve Lectures on Subjects Suggested by His Life and Work". There was no need for him to embellish the story while it was published to "cheer up" Ramanujan, since the book was published in 1940 after Ramanujan's death.

  Two great men can have different interests in the same field. It does not mean one of them had less ability. Hardy, since his early days, was fascinated by pure mathematics and rigor. Ramanujan was playing with numbers on pieces of paper since he was a child. That's why their contributions and intuitions, even though in the same broad field, are so different.

• by cortesi on 1/31/22, 1:13 AM

  I once correctly guessed a that friend's PIN was "1729", based only on the fact that he was a maths major, a huge fan of Ramanujan, and was sure to have read this story. I still cherish the look of complete confusion on his face, more than 20 years later.

• by jbandela1 on 1/31/22, 3:03 AM

  > Hardy either knew of Ramanujan’s work on this problem or noticed himself that 1729 had a special property. He wanted to cheer up his dear friend Ramanujan, who was lying deathly ill in the hospital. So he played the fool by walking in and saying that 1729 was “rather dull”.

  If this is the case, it really increases my respect for Hardy. Anybody can brag, but to willingly seem to be the fool, in order to help someone else (and notice how even in his retelling of the story, he still plays the fool for others as foil to Ramanujan) takes a really big person.

• by jimmyed on 1/31/22, 3:17 AM

  > it is the smallest number expressible as the sum of two cubes in two different ways.

  I don't understand why satisfying this completely arbitrary condition makes it interesting. That way, you can have any number be interesting.

  1730 is the smallest number greater than the smallest number expressible as the sum of two cubes in two different ways.

• by nmridul on 1/31/22, 3:39 AM

  >> in his “second notebook”. This is one of three notebooks Ramanujan left behind after his death—

  Hope the present day Mathematicians, biologist etc still use physical notebooks or non-propretary format note taking apps that will make their work accessible to others after their death.

• by texteller on 1/31/22, 9:16 AM

  Ramanujan always amazes me. Remembering my visit to the Ramanujan Museum in India, which treasures the pictures, letters, and documents focusing the greatest mathematician of the 20th Century:

  https://casualwalker.com/museum-for-the-man-who-knew-infinit...

• by johncarlosbaez on 1/30/22, 8:36 PM

  I just looked into this story, and there was more to it than we usually hear.

• by etothepii on 1/31/22, 2:05 AM

  This is a fascinating question. This is a famous story, as a Cambridge mathematician I've heard it many times but the simple question, 'did the cab reg numbers in uk in 1919 allow for a match with ".*1.*7.*2.*9.*"' is not easily answerable.