login
Number of permutations sigma such that |sigma(i+j)-sigma(i)| >= 5 for 1 <= i <= n - j, 1 <= j <= 4.
1

%I #12 Dec 03 2018 15:18:33

%S 1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,128,6320,344872

%N Number of permutations sigma such that |sigma(i+j)-sigma(i)| >= 5 for 1 <= i <= n - j, 1 <= j <= 4.

%C 2 | a(n) for n > 1.

%e a(25) = 2: [5,10,15,20,25,4,9,14,19,24,3,8,13,18,23,2,7,12,17,22,1,6,11,16,21] and its reverse.

%Y Cf. A179958, A279214, A322281.

%K nonn,more

%O 0,26

%A _Seiichi Manyama_, Dec 03 2018