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%I #8 Mar 04 2018 04:14:18
%S 5,0,3,8,2,1,6,6,7,6,1,5,9,1,8,6,7,4,9,1,8,5,4,1,7,0,2,6,4,4,8,8,8,9,
%T 4,7,1,0,8,3,7,5,9,2,2,3,9,0,2,8,1,5,6,9,3,4,4,7,2,2,9,7,1,7,9,1,2,6,
%U 5,4,4,1,0,1,3,2,6,6,9,2,1,8,5,9,4,7
%N Decimal expansion of e^(W(1) + W(3)) = 3/(W(1)*W(3)), where W is the Lambert W function (or PowerLog); see Comments.
%C The Lambert W function satisfies the functional equation e^(W(x) + W(y)) = x*y/(W(x)*W(y)) for x and y greater than -1/e, so that e^(W(1) + W(3)) = 3/(W(1)*W(3)). See A299613 for a guide to related constants.
%H G. C. Greubel, <a href="/A299621/b299621.txt">Table of n, a(n) for n = 1..10000</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/LambertW-Function.html">Lambert W-Function</a>
%e e^(W(1) + W(3)) = 5.03821667615918674918541702644888...
%t w[x_] := ProductLog[x]; x = 1; y = 3;
%t N[E^(w[x] + w[y]), 130] (* A299621 *)
%t RealDigits[3/(LambertW[1]*LambertW[3]), 10, 100][[1]] (* _G. C. Greubel_, Mar 03 2018 *)
%o (PARI) 3/(lambertw(1)*lambertw(3)) \\ _G. C. Greubel_, Mar 03 2018
%Y Cf. A299613, A299620.
%K nonn,cons,easy
%O 1,1
%A _Clark Kimberling_, Mar 01 2018