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Borwein Integrals


The Borwein integrals are the class of definite integrals defined by

 I_n=1/piint_0^inftyx^(-(n+1)/2)product_(k=1,3,...)^nsin(x/k)dx

for positive odd integers n. If J_m=int_0^inftyproduct_(j=0)^(m)sinc(x/(2j+1))dx, with sinc(t)=sin(t)/t for t!=0 and sinc(0)=1, then I_(2m+1)=J_m/[pi(2m+1)!!], where m is a nonnegative integer and !! denotes the double factorial (Borwein and Borwein 2001, pp. 74, 78, 86). These sinc function integrals satisfy J_m=pi/2 for m=0, 1, ..., 6, but J_7<pi/2. Thus the values I_n for n=1, 3, ..., 13 have unit numerators, and this pattern first fails at n=15. The sequence of values of I_n for n=1, 3, ... is given by 1/2, 1/6, 1/30, 1/210, 1/1890, 1/20790, 1/270270, 467807924713440738696537864469/1896516717212415135141110350293750000, ... (OEIS A068214 and A068215; Borwein et al. 2004, p. 98; Bailey et al. 2006). Both OEIS sequences use index m=(n-1)/2, starting at 0. Sequence OEIS A068215 gives the denominators of I_(2m+1). Sequence OEIS A068214 gives the numerators of J_m/(pi/2), which agree with the numerators of the explicitly displayed values of I_n.


See also

Infinite Cosine Product Integral, Sinc Function

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References

Bailey, D. H.; Borwein, J. M.; Kapoor, V.; and Weisstein, E. W. "Ten Problems in Experimental Mathematics." Amer. Math. Monthly 113, 481-509, 2006.Borwein, D. and Borwein, J. M. "Some Remarkable Properties of Sinc and Related Integrals." Ramanujan J. 5, 73-89, 2001. https://doi.org/10.1023/A:1011497229317.Borwein, D.; Borwein, J. M.; and Mares, B. A. Jr. "Multi-Variable Sinc Integrals and Volumes of Polyhedra." Ramanujan J. 6, 189-208, 2002.Borwein, J.; Bailey, D.; and Girgensohn, R. "Some Curious Sinc Integrals." §2.5 in Experimentation in Mathematics: Computational Paths to Discovery. Wellesley, MA: A K Peters, p. 98, 2004.Sloane, N. J. A. Sequences A068214 and A068215 in "The On-Line Encyclopedia of Integer Sequences."

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Borwein Integrals

Cite this as:

Weisstein, Eric W. "Borwein Integrals." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/BorweinIntegrals.html

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