A293044 Number of even permutations s of {1,2,...,n} such that |s(i)-i| > 1 for each i=1,2,...,n.
1, 0, 0, 0, 1, 2, 14, 104, 854, 7850, 79870, 890348, 10799871, 141647372, 1997815108, 30156348224, 485117044079, 8285798537070, 149759338727580, 2855791585334780, 57300933786123530, 1206811729692494146, 26619251746350630604, 613691499376088985144
Offset: 0
Keywords
Links
- Dmitry Efimov, Determinants of generalized binary band matrices, arXiv:1702.05655 [math.RA], 2017.
Formula
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.