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%I #48 Aug 21 2023 10:25:55
%S 4,2,4,2,6,4,0,6,8,7,1,1,9,2,8,5,1,4,6,4,0,5,0,6,6,1,7,2,6,2,9,0,9,4,
%T 2,3,5,7,0,9,0,1,5,6,2,6,1,3,0,8,4,4,2,1,9,5,3,0,0,3,9,2,1,3,9,7,2,1,
%U 9,7,4,3,5,3,8,6,3,2,1,1,1,6,5,5,1,1,6,2,6,0,2,9,8,2,9,2,4,7,1
%N Decimal expansion of square root of 18.
%C Continued fraction expansion is 4 followed by {4, 8} repeated. - _Harry J. Smith_, Jun 05 2009
%C 3*sqrt(2) = sqrt(18) is also the minimum width of the arms of the cellular automaton described in A294020. - _Omar E. Pol_, Oct 29 2017
%C Equals lambda(3) where lambda(n) = n*Product_{k=2..n-1} k^((n-k)/(n-k+1)). - _Michel Marcus_, Apr 02 2020
%H Harry J. Smith, <a href="/A010474/b010474.txt">Table of n, a(n) for n = 1..20000</a>
%H Michael Penn, <a href="https://www.youtube.com/watch?v=RsIm-OFKQUI">A nice algebra problem with complex numbers</a>, YouTube video, 2022.
%H <a href="/index/Al#algebraic_02">Index entries for algebraic numbers, degree 2</a>
%e 4.242640687119285146405066172629094235709015626130844219530039213972197....
%p evalf[100](sqrt(18)); # _Muniru A Asiru_, Feb 12 2019
%t RealDigits[Sqrt[18], 10, 100][[1]] (* _Vladimir Joseph Stephan Orlovsky_, Feb 21 2011 *)
%o (PARI) default(realprecision, 100); sqrt(18) \\ _Harry J. Smith_, Jun 03 2009 (modified by _G. C. Greubel_, Feb 14 2019)
%o (Magma) SetDefaultRealField(RealField(100)); Sqrt(18); // _G. C. Greubel_, Feb 14 2019
%o (Sage) numerical_approx(sqrt(18), digits=100) # _G. C. Greubel_, Feb 14 2019
%Y Cf. A040013 (continued fraction). - _Harry J. Smith_, Jun 03 2009
%K nonn,cons
%O 1,1
%A _N. J. A. Sloane_
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