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du Bois-Reymond Constants


duBoisReymondConstants

The constants C_n defined by

 C_n=[int_0^infty|d/(dt)((sint)/t)^n|dt]-1.
(1)

These constants can also be written as the sums

 C_n=2sum_(k=1)^infty(1+x_k^2)^(-n/2),
(2)

and

 C_n=2sum_(k=1)^infty|sinc(x_k)|^n
(3)

(E. Weisstein, Feb. 3, 2015), where x_k is the kth positive root of

 t=tant
(4)

and sinc(x) is the sinc function.

C_1 diverges, with the first few subsequent constant numerically given by

C_2 approx 0.1945280494
(5)
C_3 approx 0.02825176416
(6)
C_4 approx 0.005240704678.
(7)

Rather surprisingly, the even-ordered du Bois Reymond constants (and, in particular, C_2; Le Lionnais 1983) can be computed analytically as polynomials in e^2,

C_2=1/2(e^2-7)
(8)
C_4=1/8(e^4-4e^2-25)
(9)
C_6=1/(32)(e^6-6e^4+3e^2-98)
(10)

(OEIS A085466 and A085467) as found by Watson (1933). For positive integer n, these have the explicit formula

 C_(2n)=-(3+delta_(1n))-2Res_(x=i)[(x^2)/((1+x^2)^n(tanx-x))],
(11)

where Res denotes a complex residue and delta_(ij) is a Kronecker delta (V. Adamchik).


See also

Series, Tanc Function

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References

Finch, S. R. "Du Bois Reymond's Constants." §3.12 in Mathematical Constants. Cambridge, England: Cambridge University Press, pp. 237-240, 2003.Le Lionnais, F. Les nombres remarquables. Paris: Hermann, p. 23, 1983.Sloane, N. J. A. Sequences A085466 and A085467 in "The On-Line Encyclopedia of Integer Sequences."Watson, G. N. "Du Bois Reymond's Constants." Quart. J. ath. 4, 140-146, 1933.Young, R. M. "A Rayleigh Popular Problem." Amer. Math. Monthly 93, 660-664, 1986.

Cite this as:

Weisstein, Eric W. "du Bois-Reymond Constants." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/duBois-ReymondConstants.html

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