A268536 - cp's OEIS frontend

A268536 The number of permutations of {1,2,...,n,1,2,...,n} with the property that there are k numbers between the two k's in the set for k=1,...,n, as n runs through the positive integers congruent to -1 or 0 mod 4.

%I A268536 #10 Feb 23 2016 13:19:08
%S A268536 2,2,52,300,35584,216288,79619280,653443600,513629782560,
%T A268536 5272675722400,7598911885030976,93690316113031872,
%U A268536 223367222197529806464,3214766521218764786304
%N A268536 The number of permutations of {1,2,...,n,1,2,...,n} with the property that there are k numbers between the two k's in the set for k=1,...,n, as n runs through the positive integers congruent to -1 or 0 mod 4.
%H A268536 Ali Assarpour, Amotz Bar-Noy, Ou Liuo, <a href="http://arxiv.org/abs/1507.00315">Counting the Number of Langford Skolem Pairings</a>, arXiv:1507.00315 [cs.DM], 2015.
%Y A268536 This is A176127 without the zeros.
%K A268536 nonn
%O A268536 1,1
%A A268536 _N. J. A. Sloane_, Feb 22 2016

cp's OEIS Frontend

A268536 The number of permutations of {1,2,...,n,1,2,...,n} with the property that there are k numbers between the two k's in the set for k=1,...,n, as n runs through the positive integers congruent to -1 or 0 mod 4.