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%I #46 Feb 19 2024 14:17:53
%S 7,9,7,8,8,4,5,6,0,8,0,2,8,6,5,3,5,5,8,7,9,8,9,2,1,1,9,8,6,8,7,6,3,7,
%T 3,6,9,5,1,7,1,7,2,6,2,3,2,9,8,6,9,3,1,5,3,3,1,8,5,1,6,5,9,3,4,1,3,1,
%U 5,8,5,1,7,9,8,6,0,3,6,7,7,0,0,2,5,0,4,6,6,7,8,1,4,6,1,3,8,7,2,8,6,0,6,0
%N Decimal expansion of sqrt(2/Pi).
%C This is the limit of (n+1)!!/n!!/n^(1/2) at n_even->inf.
%C Expected value of |x - mu|/sigma for normal distribution with mean mu and standard deviation sigma (i.e., the normalized mean absolute deviation). - _Stanislav Sykora_, Jun 30 2017
%H Vincenzo Librandi, <a href="/A076668/b076668.txt">Table of n, a(n) for n = 0..1000</a>
%H Harmann König, Carsten Schütt, and Nicole Tomczak-Jaegermann, <a href="https://doi.org/10.1515/crll.1999.511.1">Projection constants of symmetric spaces and variants of Khintchine's inequality</a>, J. reine angew. Math. 511 (1999), pp. 1-42.
%H <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>
%F Equals A087197*A002193. - _R. J. Mathar_ Feb 05 2009
%F Equals integral_{-infinity..infinity} (1-erf(x)^2)/2 dx. - _Jean-François Alcover_, Feb 25 2015
%e 0.79788456080286535587989211986876373695171726232986931533...
%t RealDigits[Sqrt[2/Pi],10,120][[1]] (* _Harvey P. Dale_, Feb 05 2012 *)
%o (Magma) pi:=Sqrt(2/Pi(RealField(110))); Reverse(Intseq(Floor(10^110*pi))); // _Vincenzo Librandi_, Jul 01 2017
%o (PARI) sqrt(2/Pi) \\ _G. C. Greubel_, Sep 23 2017
%Y Cf. A004730, A004731, A019727, A060294 (Buffon's constant 2/Pi), A092678 (probable error).
%K nonn,cons
%O 0,1
%A _Zak Seidov_, Oct 25 2002
%E More terms and better description from _Benoit Cloitre_ and _Michael Somos_, Oct 29 2002
%E Leading zero removed, offset changed by _R. J. Mathar_, Feb 05 2009
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