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 A047162 #8 Apr 11 2021 22:15:09
%S A047162 0,0,0,2,3,9,12,30,40,100,135,335,455,1127,1540,3822,5250,13050,18000,
%T A047162 44802,62007,154517,214467,534963,744315,1858155,2590679,6472167,
%U A047162 9039823,22597759,31612324,79067374,110761494,277164294,388742706,973184312,1366460867,3422117189
%N A047162 Number of nonempty subsets of {1,2,...,n} in which exactly 2/3 of the elements are <= n/2.
%H A047162 Andrew Howroyd, <a href="/A047162/b047162.txt">Table of n, a(n) for n = 1..1000</a>
%F A047162 a(n) = Sum_{k>=1} binomial(floor(n/2), 2*k)*binomial(ceiling(n/2), k). - _Andrew Howroyd_, Apr 11 2021
%o A047162 (PARI) a(n) = {my(m=n\2); sum(k=1, n\4, binomial(m, 2*k)*binomial(n-m, k))} \\ _Andrew Howroyd_, Apr 11 2021
%Y A047162 Cf. A047161.
%K A047162 nonn
%O A047162 1,4
%A A047162 _Clark Kimberling_
%E A047162 Terms a(35) and beyond from _Andrew Howroyd_, Apr 11 2021