Tuesday, 10 October 2006

Ramanujan's interesting number

I have a friend called T D Ranga Ramanujan (or I used to have: I lost contact with him some years ago). It's not an uncommon name in India and he once told me to my disappointment that he was not a relation of Srinivasa Ramanujan, said to be the greatest mathematical prodigy that the world has ever seen.

C. P. Snow and many others have told the extraordinary story of how the British mathematician G. H. Hardy discovered Ramanujan’s genius in 1914 and brought this poor self-taught Madras clerk to Trinity College Cambridge, where he later received the highest possible honours, including a Fellowship of the Royal Society at the age of thirty. But he soon became ill and returned to India where he died in 1919 aged 33, probably of tuberculosis.

The best-known anecdote about him was told by Hardy:
I remember once going to see him when he was ill at Putney. I had ridden in taxicab number 1729 and remarked that the number seemed to me rather a dull one, and that I hoped it was not an unfavourable omen. "No, Hardy!" he replied, "No, Hardy! It is a very interesting number; it is the smallest number expressible as the sum of two cubes in two different ways”.
This was not a lightning calculation on Ramanujan’s part: he had referred to this and many other characteristics of the number (now called the Hardy-Ramanujan number and a taxicab number) in his notebooks written years earlier.

An Indo-British feature film on his life will begin shooting in 2007 in Tamil Nadu state and Cambridge.

Wikipedia covers all this in detail here and here. It also has an article describing an internal dispute among its contributors which illustrates the difficulties of producing an online encyclopedia which anyone can edit, particularly when mathematicians are involved—they will even argue about what is interesting and what is dull: reading that discussion carefully will give you a buzzing sensation in the head.

[By the way, 1729 = 1³ + 12³ and also 9³+ 10³]

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