%I
%S 2,1,1,2,4,7,14,29,61,129,282,623,1400,3189,7347,17101,40167,95110,
%T 226841,544555,1314983,3192458,7788521,19086807,46968280,116019696,
%U 287602234,715281652,1784383956,4464139806
%N Floor of the expected value of number of trials until exactly one cell is empty in a random distribution of n balls in n cells.
%C Also floor of the expected value of number of trials until we have n1 distinct symbols in a random sequence on n symbols of length n. A055775 corresponds to zero cells empty.
%D W. Feller, An Introduction to Probability Theory and its Applications, 2nd ed, Wiley, New York, 1965, (2.4) p. 92. (Occupancy problems)
%H Washington Bomfim, <a href="/A210112/b210112.txt">Table of n, a(n) for n = 2..100</a>
%F With m = 1, a(n) = floor(n^n/(binomial(n,m)_Sum{v=0..nm1}((1)^v*binomial(nm,v) (nmv)^n)))
%e For n=2, with symbols 0 and 1, the 2^2 sequences on 2 symbols of length 2 can be represented by 00, 01, 10, and 11. We have 2 sequences with a unique symbol, so a(2) = floor(4/2) = 2.
%Y Cf. A055775, A209899, A209900, A210113, A210114, A210115, A210116.
%K nonn
%O 2,1
%A _Washington Bomfim_, Mar 18 2012
