A293044 - OEIS

%I #6 Oct 09 2017 23:21:34

%S 1,0,0,0,1,2,14,104,854,7850,79870,890348,10799871,141647372,

%T 1997815108,30156348224,485117044079,8285798537070,149759338727580,

%U 2855791585334780,57300933786123530,1206811729692494146,26619251746350630604,613691499376088985144

%N Number of even permutations s of {1,2,...,n} such that |s(i)-i| > 1 for each i=1,2,...,n.

%H Dmitry Efimov, <a href="https://arxiv.org/abs/1702.05655">Determinants of generalized binary band matrices</a>, arXiv:1702.05655 [math.RA], 2017.

%F a(n) = (A001883(n) + d(n))/2, where d(n) = (3-n)/3 if n = 0 mod 3, d(n) = (n-1)/3 if n = 1 mod 3, d(n) = 0 if n = 2 mod 3.

%Y Cf. A001883, A293045.

%K nonn

%O 0,6

%A _Eric M. Schmidt_, Oct 09 2017