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%I #15 Dec 01 2018 08:21:56
%S 1,1,5,36,466,8942,240366,8576860,392952468,22470271108
%N The number of permutations of {1,2,...,n,1,2,...,n} with the property that there are k or fewer numbers between the two k's in the set for k=1,...,n.
%e In case of n = 2.
%e | permutation
%e --+-------------
%e 1 | [1, 1, 2, 2]
%e 2 | [1, 2, 1, 2]
%e 3 | [2, 1, 1, 2]
%e 4 | [2, 1, 2, 1]
%e 5 | [2, 2, 1, 1]
%Y Cf. A176127, A322179.
%K nonn,more
%O 0,3
%A _Seiichi Manyama_, Nov 30 2018
%E a(9) from _Alois P. Heinz_, Nov 30 2018