This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A210114 #9 May 05 2013 16:28:36
%S A210114 64,10,4,2,2,2,2,3,5,7,11,18,31,55,100,185,348,670,1311,2606,5254,
%T A210114 10734,22196,46407,98023,209009,449580,974963,2130442,4688533,
%U A210114 10387113,23156162,51926745,117090391,265413053
%N A210114 Floor of the expected value of number of trials until exactly three cells are empty in a random distribution of n balls in n cells.
%C A210114 Also floor of the expected value of number of trials until we have n-3 distinct symbols in a random sequence on n symbols of length n. A055775 corresponds to zero cells empty.
%D A210114 W. Feller, An Introduction to Probability Theory and its Applications, 2nd ed, Wiley, New York, 1965, (2.4) p. 92. (Occupancy problems)
%H A210114 Washington Bomfim, <a href="/A210114/b210114.txt">Table of n, a(n) for n = 4..100</a>
%F A210114 With m = 3, a(n) = floor(n^n/(binomial(n,m)*_Sum{v=0..n-m-1}((-1)^v*binomial(n-m,v)*(n-m-v)^n)))
%e A210114 For n=4, there are 4^4 = 256 sequences on 4 symbols of length 4. Only 4 sequences have a unique symbol, so a(4) = floor(256/4) = 64.
%Y A210114 Cf. A055775, A209899, A209900, A210112, A210113, A210115, A210116.
%K A210114 nonn
%O A210114 4,1
%A A210114 _Washington Bomfim_, Mar 18 2012