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 A324352 #11 May 03 2021 08:17:08
%S A324352 0,1,5,28,179,1306,10757,98932,1006007,11214406,136041329,1784556808,
%T A324352 25174694723,380087428618,6115760751869,104481070398556,
%U A324352 1888837397941487,36026457717419662,723015306101706857,15230427461356523056,336009169512596054459
%N A324352 Total number of occurrences of 2 in the (signed) displacement sets of all permutations of [n+2] divided by 2!.
%H A324352 Alois P. Heinz, <a href="/A324352/b324352.txt">Table of n, a(n) for n = 0..448</a>
%H A324352 Wikipedia, <a href="https://en.wikipedia.org/wiki/Permutation">Permutation</a>
%F A324352 E.g.f.: (1-exp(-x))/(1-x)^3.
%F A324352 a(n) = -1/2! * Sum_{j=1..n} (-1)^j * binomial(n,j) * (n+2-j)!.
%F A324352 a(n) = A306234(n+2,2).
%p A324352 a:= n-> (k-> -add((-1)^j*binomial(n, j)*(n+k-j)!, j=1..n)/k!)(2):
%p A324352 seq(a(n), n=0..23);
%t A324352 m = 23;
%t A324352 CoefficientList[(1-Exp[-x])/(1-x)^3 + O[x]^(m+1), x]*Range[0, m]! (* _Jean-François Alcover_, May 03 2021 *)
%Y A324352 Column k=2 of A324362.
%Y A324352 Cf. A306234.
%K A324352 nonn
%O A324352 0,3
%A A324352 _Alois P. Heinz_, Feb 23 2019