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%I #12 Aug 03 2014 14:01:40
%S 0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,3,3,3,3,3,3,3,4,4,4,4,
%T 4,4,4,5,5,5,5,5,5,5,5,6,6,6,6,6,6,6,7,7,7,7,7,7,7,7,8,8,8,8,8,8,8,9,
%U 9,9,9,9,9,9,10,10,10,10,10,10,10,10,11,11
%N Floor of the expected number of empty cells in a random placement of 2n balls into n cells.
%D W. Feller, An Introduction to Probability Theory and its Applications, 2nd ed, Wiley, New York, 1965, p. 226.
%F a(n) = floor(n*(1-1/n)^(2n)).
%t Table[Floor[n*(1 - 1/n)^(2 n)], {n, 100}] (* _T. D. Noe_, Mar 15 2012 *)
%Y Cf. A209900.
%K nonn
%O 1,16
%A _Washington Bomfim_, Mar 14 2012