OFFSET
1,1
LINKS
Eric Weisstein's MathWorld, Planck's Radiation Function
FORMULA
(15*(W(-(5/e^5)) + 5)^5)/((-1 + exp(W(-(5/e^5)) + 5))*Pi^4), where W is the LambertW function (also known as ProductLog).
EXAMPLE
3.2648034339755571402288131198557638278982761871385361958956956...
MATHEMATICA
f[x_] := 15/(Pi^4*x^5*(Exp[1/x] - 1)); xmax = 1/(ProductLog[-5*Exp[-5]] + 5); RealDigits[f[xmax], 10, 105] // First
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Jean-François Alcover, Jul 15 2014
STATUS
approved