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 A322179 #15 Dec 01 2018 08:21:41
%S A322179 1,0,0,2,40,1070,38936,1896220,119912476,9587033840
%N A322179 The number of permutations of {1,2,...,n,1,2,...,n} with the property that there are k or more numbers between the two k's in the set for k=1,...,n.
%e A322179 In case of n = 3.
%e A322179 | permutation
%e A322179 --+-------------------
%e A322179 1 | [2, 3, 1, 2, 1, 3]
%e A322179 2 | [3, 1, 2, 1, 3, 2]
%Y A322179 Cf. A176127, A322180.
%K A322179 nonn,more
%O A322179 0,4
%A A322179 _Seiichi Manyama_, Nov 30 2018
%E A322179 a(9) from _Alois P. Heinz_, Nov 30 2018