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A048046 Number of nonempty subsets of {1,2,...,n} in which exactly 4/5 of the elements are <= (n+1)/3. 1

%I #7 Apr 16 2019 15:07:14

%S 0,0,0,0,0,0,0,0,0,0,7,8,9,45,50,55,165,180,195,455,490,525,1155,1240,

%T 1326,3366,3645,3933,11685,12750,13860,41580,45375,49335,138391,

%U 150524,163175,433875,470665,509067,1347255,1461278,1580761

%N Number of nonempty subsets of {1,2,...,n} in which exactly 4/5 of the elements are <= (n+1)/3.

%H Robert Israel, <a href="/A048046/b048046.txt">Table of n, a(n) for n = 1..5710</a>

%p f:= proc(n) local k,j;

%p k:= floor((n+1)/3);

%p add(binomial(k,4/5*j)*binomial(n-k,1/5*j),j=5..n,5)

%p end proc:

%p map(f, [$1..100]); # _Robert Israel_, Apr 16 2019

%K nonn

%O 1,11

%A _Clark Kimberling_

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Last modified March 1 18:30 EST 2024. Contains 370443 sequences. (Running on oeis4.)