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 A334780 #9 May 18 2020 10:48:40
%S A334780 1,8,168,6336,360000,28728000,3067243200,422479411200,72968229734400,
%T A334780 15446903472000000,3933958530902400000,1186723982675911680000,
%U A334780 418497083472072084480000,170595438771094235458560000,79604772050991371184000000000,42160341403338557272473600000000
%N A334780 Total number of local maxima in all permutations of 2 indistinguishable copies of 1..n arranged in a circle.
%H A334780 Andrew Howroyd, <a href="/A334780/b334780.txt">Table of n, a(n) for n = 1..100</a>
%F A334780 a(n) = Sum_{k=1..n} k*A334778(n,k).
%o A334780 (PARI) \\ CircPeaksBySig defined in A334778.
%o A334780 a(n)={my(u=CircPeaksBySig(vector(n, i, 2), [1..n])); sum(k=1, #u, k*u[k])}
%Y A334780 Cf. A334778.
%K A334780 nonn
%O A334780 1,2
%A A334780 _Andrew Howroyd_, May 13 2020