# Tirukkannapuram Vijayaraghavan

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Thirukannapuram Vijayaraghavan
Born30 November 1902
Died20 April 1955 (aged 52)
Occupationmathematician

Tirukkannapuram Vijayaraghavan (Tamil : திருக்கண்ணபுரம் விஜயராகவன்; 30 November 1902 – 20 April 1955) was an Indian mathematician from the Madras region. He worked with G. H. Hardy when he went to Oxford in mid-1920s on Pisot–Vijayaraghavan numbers. He was a fellow of Indian Academy of Sciences elected in the year 1934.

Vijayaraghavan was well versed in Sanskrit and Tamil. He was a close friend of André Weil. He served with him in Aligarh Muslim University. He later moved to the University of Dhaka in protest at Weil's firing from AMU. [1]

Vijayaraghavan proved a special case of Herschfeld's theorem on nested radicals: [2] For ${\displaystyle a_{n}>0}$

${\displaystyle {\sqrt {a_{1}+{\sqrt {a_{2}+{\sqrt {a_{3}+{\sqrt {a_{4}+\cdots }}}}}}}}}$

converges if and only if

${\displaystyle {\overline {\lim }}(\log a_{n})/2^{n}<+\infty ,}$

where ${\displaystyle {\overline {\lim }}}$ denotes the limit superior.

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## References

1. Ramanujan, S. Collected Papers of Srinivasa Ramanujan (Ed. G. H. Hardy, P. V. S. Aiyar, and B. M. Wilson). Providence, RI: American Mathematical Society (2000), p. 348.