Simple Continued Fraction

A simple continued fraction is a special case of a generalized continued fraction for which the partial numerators are equal to unity, i.e., a_n=1 for all n=1, 2, .... A simple continued fraction is therefore an expression of the form


When used without qualification, the term "continued fraction" is often used to mean "simple continued fraction" or, more specifically, regular (i.e., a simple continued fraction whose partial denominators b_0, b_1, ... are positive integer; Rockett and Szüsz 1992, p. 3). Care must therefore be taken to identify the intended meaning based on the context in which such terminology is encountered.

A simple continued fraction can be written in a compact abbreviated notation as




where N may be finite (for a finite continued fraction) or infty (for an infinite continued fraction). In contexts where only simple continued fractions are considered, the partial denominators are often denoted [a_0;a_1,a_2,...] instead of [b_0;b_1,b_2,...] (e.g., Rockett and Szüsz 1992, p. 3), a practice which unfortunately conflicts with the common notation for generalized continued fractions in which a_n denotes a partial numerator.

Further care is needed when encountering bracket notation for simple continued fractions since some authors replace the semicolon with a normal comma and begin indexing the terms at b_1 instead of b_0, writing [b_0,b_1,b_2,...] instead of [b_0;b_1,b_2,...] or b_0+[b_1,b_2,...], causing ambiguity in the meaning of the initial term and resulting in the parity of certain fundamental results in continued fraction theory to be reversed. To complicate matters a bit further, Gaussian brackets use the notation [a_1,a_2,...,a_n] to denote a different (but closely related) combination of partial denominators.

The terms b_0 through b_(n-1) of the simple continued fraction of a number x can be computed in the Wolfram Language using the command ContinuedFraction[x, n]. Similarly, the n convergent of simple continued fraction with partial denominators b_k can be continued using ContinuedFractionK[a[k], {k, n}], where n may be Infinity.

See also

Continued Fraction, Convergent, Gaussian Brackets, Partial Denominator, Partial Numerator, Regular Continued Fraction

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Rockett, A. M. and Szüsz, P. Continued Fractions. New York: World Scientific, 1992.

Referenced on Wolfram|Alpha

Simple Continued Fraction

Cite this as:

Weisstein, Eric W. "Simple Continued Fraction." From MathWorld--A Wolfram Web Resource.

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