A259784 - OEIS

%I #25 May 05 2019 08:58:04

%S 1,0,0,0,1,0,0,0,2,0,0,1,3,5,0,0,0,6,18,20,0,0,1,12,44,111,97,0,0,0,

%T 24,116,396,744,574,0,0,1,44,331,1285,3628,5571,3973,0,0,0,84,932,

%U 4312,15038,34948,46662,31520,0,0,1,159,2532,15437,59963,181193,359724,434127,281825,0

%N Number T(n,k) of permutations p of [n] with no fixed points where the maximal displacement of an element equals k; triangle T(n,k), n>=0, 0<=k<=n, read by rows.

%H Alois P. Heinz, <a href="/A259784/b259784.txt">Rows n = 0..20, flattened</a>

%F T(n,k) = A259776(n,k) - A259776(n,k-1) for k>0, T(n,0) = A000007(n).

%e Triangle T(n,k) begins:

%e   1;

%e   0, 0;

%e   0, 1,  0;

%e   0, 0,  2,   0;

%e   0, 1,  3,   5,    0;

%e   0, 0,  6,  18,   20,    0;

%e   0, 1, 12,  44,  111,   97,    0;

%e   0, 0, 24, 116,  396,  744,  574,    0;

%e   0, 1, 44, 331, 1285, 3628, 5571, 3973, 0;

%p b:= proc(n, s, k) option remember; `if`(n=0, 1, `if`(n+k in s,

%p       b(n-1, (s minus {n+k}) union `if`(n-k>1, {n-k-1}, {}), k),

%p       add(`if`(j=n, 0, b(n-1, (s minus {j}) union

%p       `if`(n-k>1, {n-k-1}, {}), k)), j=s)))

%p     end:

%p A:= (n, k)-> `if`(k=0, `if`(n=0, 1, 0), b(n, {$max(1, n-k)..n}, k)):

%p T:= (n, k)-> A(n, k) -`if`(k=0, 0, A(n, k-1)):

%p seq(seq(T(n, k), k=0..n), n=0..12);

%t b[n_, s_, k_] := b[n, s, k] = If[n==0, 1, If[MemberQ[s, n+k], b[n-1, (s ~Complement~ {n+k}) ~Union~ If[n-k>1, {n-k-1}, {}], k], Sum[If[j==n, 0, b[n-1, (s ~Complement~ {j}) ~Union~ If[n-k>1, {n-k-1}, {}], k]], {j, s}]] ];

%t A[n_, k_] := If[k == 0, If[n == 0, 1, 0], b[n, Range[Max[1, n-k], n], k]];

%t T[n_, k_] :=  A[n, k] - If[k == 0, 0, A[n, k-1]];

%t Table[T[n, k], {n, 0, 12}, {k, 0, n}] // Flatten (* _Jean-François Alcover_, May 05 2019, after _Alois P. Heinz_ *)

%Y Rows sums give A000166.

%Y Column k=0 and main diagonal give A000007.

%Y Columns k=1-10 give: A059841 (for n>0), A321048, A321049, A321050, A321051, A321052, A321053, A321054, A321055, A321056.

%Y First lower diagonal gives A259834.

%Y T(2n,n) gives A259785.

%Y Cf. A259776.

%K nonn,tabl

%O 0,9

%A _Alois P. Heinz_, Jul 05 2015