cp's OEIS Frontend

A087198 Decimal expansion of 1/(2*sqrt(Pi)).

%I A087198 #19 Sep 28 2022 14:01:50
%S A087198 2,8,2,0,9,4,7,9,1,7,7,3,8,7,8,1,4,3,4,7,4,0,3,9,7,2,5,7,8,0,3,8,6,2,
%T A087198 9,2,9,2,2,0,2,5,3,1,4,6,6,4,4,9,9,4,2,8,4,2,2,0,4,2,8,6,0,8,5,5,3,2,
%U A087198 1,2,3,4,2,2,0,7,4,6,7,0,7,2,4,3,3,7,1,8,3,0,1,0,1,0,5,3,6,8,1,7,2,1,5,1,4
%N A087198 Decimal expansion of 1/(2*sqrt(Pi)).
%C A087198 Radius of a sphere with surface area 1.
%C A087198 According to Fouad (2004), to simulate the distance of a sound source under free field conditions, one can multiply "the waveform directly by a gain factor that is the square root of the intensity," which can be computed with the formula D = sqrt(1/(4 * Pi * d^2)) = 1/(3.55 * d), where d is the distance between the sound source and the listener and 3.55 is approximately 10(sqrt(Pi)/5) (A019707) (equation 15 in the chapter), though "in practice we usually drop the constant multiplier" (4 * Pi). If the distance is one unit, then D works out to this number. - _Alonso del Arte_, Jun 10 2012
%D A087198 Hesham Fouad, "Spatialization with Stereo Loudspeakers: Understanding Balance, Panning and Distance Attenuation" in Audio Anecdotes II: Tools, Tips, and Techniques for Digital Audio, K. Greenebaum & R. Barzel, eds. Wellesley, Massachusetts: A K Peters (2004): 150 - 153
%H A087198 G. C. Greubel, <a href="/A087198/b087198.txt">Table of n, a(n) for n = 0..5000</a>
%H A087198 <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>
%F A087198 1/(2 * sqrt(Pi)) = sqrt(1/(4 * Pi)).
%e A087198 0.28209479177387814347...
%t A087198 RealDigits[Sqrt[1/(4Pi)], 10, 100][[1]] (* _Alonso del Arte_, Jun 10 2012 *)
%o A087198 (PARI) sqrt(1/(4*Pi)) \\ _G. C. Greubel_, Jan 09 2017
%Y A087198 Cf. A086201, A087197, A087199.
%K A087198 cons,easy,nonn
%O A087198 0,1
%A A087198 _Sven Simon_, Aug 24 2003