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%I #9 Sep 08 2020 05:49:30
%S 1,1,8,4,1,9,7,2,3,7,6,6,7,2,9,7,1,5,3,9,5,4,7,3,4,9,5,7,3,7,1,1,0,6,
%T 0,2,6,3,2,5,5,9,8,0,5,1,7,3,5,7,6,1,7,2,6,5,6,4,1,5,9,4,4,8,2,0,3,0,
%U 7,0,1,0,4,3,2,7,5,3,1,6,7,2,0,9,5,3,8,5,8,7,7,1,5,5,7,5,3,9,1,0,4,0,3,0,2
%N Decimal expansion of first inflection point of Planck's radiation function.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/PlancksRadiationFunction.html">Planck's Radiation Function</a>
%e 0.11841972376672971539...
%t f[x_] := 1/(x^5*(E^(1/x)-1)); RealDigits[x /. FindRoot[f''[x], {x, 1/10}, WorkingPrecision -> 110], 10, 105][[1]] (* _Amiram Eldar_, Sep 08 2020 *)
%Y Cf. A133838, A133840.
%K nonn,cons
%O 0,3
%A _Eric W. Weisstein_, Sep 26 2007