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Outline

Newton's Formula and the Continued Fraction Expansion of √d

2001, Experimental Mathematics

https://doi.org/10.1080/10586458.2001.10504435

Abstract

It is known that if the period s(d) of the continued fraction expansion of √ d satisfies s(d) ≤ 2, then all Newton's approximants R n = 1 2 ( pn qn + dqn pn ) are convergents of √ d, and moreover we have R n = p2n+1 q2n+1 for all n ≥ 0. Motivated with this fact we define two numbers The question is how large the quantities |j| and b can be. We prove that |j| is unbounded and give some examples which support a conjecture that b is unbounded too. We also discuss the magnitude of |j| and b compared with d and s(d).

References (2)

  1. Clemens et al. 1995] L. E. Clemens, K. D. Merrill and D. W. Roeder, "Continued fractions and series", J. Number Theory 54 (1995), 309-317. [Cohn 1977] J. H. E. Cohn, "The length of the period of the simple continued fraction of d 1/2 ", Pacific J. Math. 71 (1977), 21-32. [Elezović 1997] N. Elezović, "A note on continued fractions of quadratic irrationals", Math. Commun. 2 (1997), 27-33. [Frank 1962] E. Frank, "On continued fraction expansions for binomial quadratic surds", Numer. Math. 4 (1962), 85-95. [Komatsu 1999] T. Komatsu, "Continued fractions and Newton's ap- proximants", Math. Commun. 4 (1999), 167-176. [Mikusiński 1954] J. Mikusiński, "Sur la méthode d'approximation de Newton", Ann. Polon. Math. 1 (1954), 184-194. [Patterson and Williams 1985] C. D. Patterson and H. C. Williams, "Some periodic continued fractions with long periods", Math. Comp. 44 (1985), 523-532. [Perron 1954] O. Perron, Die Lehre von den Kettenbrüchen, Teubner, Stuttgart, 1954. [Schmidt 1980] W. M. Schmidt, Diophantine Approximation, Lecture Notes in Math. 785, Springer, Berlin, 1980. [Sharma 1959] A. Sharma, "On Newton's method of approximation", Ann. Polon. Math. 6 (1959), 295-300. [Sierpiński 1987] W. Sierpiński, Elementary Theory of Numbers, PWN, Warszawa; North-Holland, Amsterdam, 1987. [Williams 1981] H. C. Williams, "A numerical inverstigation into the length of the period of the continued fraction expansion of √ d", Math.
  2. Comp. 36 (1981), 593-601.