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%I #9 Apr 11 2021 22:15:23
%S 0,0,0,0,0,3,4,16,20,50,60,135,161,392,476,1232,1512,3864,4740,11850,
%T 14520,36300,44572,112519,138567,351351,433433,1098188,1355900,
%U 3433703,4243148,10758608,13308416,33794504,41843256,106344792,131772372,335061789,415445184,1056924666
%N Number of nonempty subsets of {1,2,...,n} in which exactly 3/4 of the elements are <= n/2.
%H Andrew Howroyd, <a href="/A047164/b047164.txt">Table of n, a(n) for n = 1..500</a>
%F a(n) = Sum_{k>=1} binomial(floor(n/2), 3*k)*binomial(ceiling(n/2), k). - _Andrew Howroyd_, Apr 11 2021
%o (PARI) a(n) = {my(m=n\2); sum(k=1, m\3, binomial(m, 3*k)*binomial(n-m, k))} \\ _Andrew Howroyd_, Apr 11 2021
%Y Cf. A047161, A047163.
%K nonn
%O 1,6
%A _Clark Kimberling_
%E Terms a(35) and beyond from _Andrew Howroyd_, Apr 11 2021
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