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►If we add and to this set of , then the resulting closed formula is the frequently-used Clenshaw–Curtisformula, whose weights are positive and given by
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►For detailed comparisons of the Clenshaw–Curtisformula with Gauss quadrature (§3.5(v)), see Trefethen (2008, 2011).
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►A comparison of several methods, including an extension of the Clenshaw–Curtisformula (§3.5(iv)), is given in Evans and Webster (1999).
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►Curtis (1964a, §10) describes the use of series, radial integration, and other methods to generate the tables listed in §33.24.
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►A set of consistent second-order WKBJ formulas is given by Burgess (1963: in Eq.
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I. S. Reed, D. W. Tufts, X. Yu, T. K. Truong, M. T. Shih, and X. Yin (1990)Fourier analysis and signal processing by use of the Möbius inversion formula.
IEEE Trans. Acoustics, Speech, Signal Processing38, pp. 458–470.
K. Reinsch and W. Raab (2000)Elliptic Integrals of the First and Second Kind – Comparison of Bulirsch’s and Carlson’s Algorithms for Numerical Calculation.
In Special Functions (Hong Kong, 1999), C. Dunkl, M. Ismail, and R. Wong (Eds.),
pp. 293–308.
C. W. Clenshaw, D. W. Lozier, F. W. J. Olver, and P. R. Turner (1986)Generalized exponential and logarithmic functions.
Comput. Math. Appl. Part B12 (5-6), pp. 1091–1101.
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►(Other normalizations for and can be found in the literature, but most formulas—including connection formulas—are unaffected since and are invariant.)
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►►►Figure 28.5.1:
for and (for comparison) .
Magnify►►►Figure 28.5.2:
for and (for comparison) .
Magnify►►►Figure 28.5.3:
for and (for comparison) .
Magnify►►►Figure 28.5.4:
for and (for comparison) .
Magnify
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►However, for applications in which the OP’s appear only as terms in series expansions (compare §18.18(i)) the need to compute them can be avoided altogether by use instead of Clenshaw’s algorithm (§3.11(ii)) and its straightforward generalization to OP’s other than Chebyshev.
For further information see Clenshaw (1955), Gautschi (2004, §§2.1, 8.1), and Mason and Handscomb (2003, §2.4).
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A. Poquérusse and S. Alexiou (1999)Fast analytic formulas for the modified Bessel functions of imaginary order for spectral line broadening calculations.
J. Quantit. Spec. and Rad. Trans.62 (4), pp. 389–395.
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►Subsequently, formulas typified by (29.6.4) can be applied to compute the coefficients of the Fourier expansions of the corresponding Lamé functions by backward recursion followed by application of formulas typified by (29.6.5) and (29.6.6) to achieve normalization; compare §3.6.
…The Fourier series may be summed using Clenshaw’s algorithm; see §3.11(ii).
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►§29.15(i) includes formulas for normalizing the eigenvectors.
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