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%I #29 Aug 21 2023 10:33:58
%S 4,4,7,2,1,3,5,9,5,4,9,9,9,5,7,9,3,9,2,8,1,8,3,4,7,3,3,7,4,6,2,5,5,2,
%T 4,7,0,8,8,1,2,3,6,7,1,9,2,2,3,0,5,1,4,4,8,5,4,1,7,9,4,4,9,0,8,2,1,0,
%U 4,1,8,5,1,2,7,5,6,0,9,7,9,8,8,2,8,8,2,8,8,1,6,7,5,7,5,6,4,5,4,9,9,3,9,0,1
%N Decimal expansion of square root of 20.
%C Continued fraction expansion is 4 followed by {2, 8} repeated. - _Harry J. Smith_, Jun 03 2009
%H Harry J. Smith, <a href="/A010476/b010476.txt">Table of n, a(n) for n = 1..20000</a>
%H <a href="/index/Al#algebraic_02">Index entries for algebraic numbers, degree 2</a>
%F sqrt(20) = 2*sqrt(5). - _Alonso del Arte_, Jun 26 2015
%F Equals Sum_{k>=0} binomial(2*k,k) * k/5^k. - _Amiram Eldar_, Aug 03 2020
%e 4.472135954999579392818347337462552470881236719223051448541794490821041....
%t RealDigits[N[Sqrt[20], 100]][[1]] (* _Vladimir Joseph Stephan Orlovsky_, Feb 21 2011 *)
%o (PARI) default(realprecision, 20080); x=sqrt(20); for (n=1, 20000, d=floor(x); x=(x-d)*10; write("b010476.txt", n, " ", d)); \\ _Harry J. Smith_, Jun 03 2009
%Y Except for offset, same as A020762.
%Y Cf. A040015 (continued fraction). - _Harry J. Smith_, Jun 03 2009
%Y Cf. A002163 (decimal expansion of square root of 5).
%K nonn,cons,easy
%O 1,1
%A _N. J. A. Sloane_
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