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 A306209 Number A(n,k) of permutations of [n] within distance k of a fixed permutation; square array A(n,k), n>=0, k>=0, read by antidiagonals. 15
 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 3, 1, 1, 1, 2, 6, 5, 1, 1, 1, 2, 6, 14, 8, 1, 1, 1, 2, 6, 24, 31, 13, 1, 1, 1, 2, 6, 24, 78, 73, 21, 1, 1, 1, 2, 6, 24, 120, 230, 172, 34, 1, 1, 1, 2, 6, 24, 120, 504, 675, 400, 55, 1, 1, 1, 2, 6, 24, 120, 720, 1902, 2069, 932, 89, 1, 1, 1, 2, 6, 24, 120, 720, 3720, 6902, 6404, 2177, 144, 1 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,9 COMMENTS A(n,k) counts permutations p of [n] such that |p(j)-j| <= k for all j in [n]. LINKS Alois P. Heinz, Antidiagonals n = 0..36, flattened Torleiv Kløve, Spheres of Permutations under the Infinity Norm - Permutations with limited displacement, Reports in Informatics, Department of Informatics, University of Bergen, Norway, no. 376, November 2008. Torleiv Kløve, Generating functions for the number of permutations with limited displacement, Electron. J. Combin., 16 (2009), #R104. FORMULA A(n,k) = Sum_{j=0..k} A130152(n,j) for n > 0, A(0,k) = 1. EXAMPLE A(4,1) = 5: 1234, 1243, 1324, 2134, 2143. A(5,2) = 31: 12345, 12354, 12435, 12453, 12534, 12543, 13245, 13254, 13425, 13524, 14235, 14253, 14325, 14523, 21345, 21354, 21435, 21453, 21534, 21543, 23145, 23154, 24135, 24153, 31245, 31254, 31425, 31524, 32145, 32154, 34125. Square array A(n,k) begins: 1, 1, 1, 1, 1, 1, 1, 1, 1, ... 1, 1, 1, 1, 1, 1, 1, 1, 1, ... 1, 2, 2, 2, 2, 2, 2, 2, 2, ... 1, 3, 6, 6, 6, 6, 6, 6, 6, ... 1, 5, 14, 24, 24, 24, 24, 24, 24, ... 1, 8, 31, 78, 120, 120, 120, 120, 120, ... 1, 13, 73, 230, 504, 720, 720, 720, 720, ... 1, 21, 172, 675, 1902, 3720, 5040, 5040, 5040, ... 1, 34, 400, 2069, 6902, 17304, 30960, 40320, 40320, ... MATHEMATICA A[0, _] = 1; A[n_ /; n > 0, k_] := A[n, k] = Permanent[Table[If[Abs[i - j] <= k, 1, 0], {i, 1, n}, {j, 1, n}]]; Table[A[n - k, k], {n, 0, 12}, {k, n, 0, -1 }] // Flatten (* Jean-François Alcover, Oct 18 2021, after Alois P. Heinz in A130152 *) CROSSREFS Columns k=0..10 give: A000012, A000045(n+1), A002524, A002526, A072856, A154654, A154655, A154656, A154657, A154658, A154659. Rows n=1-2 give: A000012, A040000. Main diagonal gives A000142. A(2n,n) gives A048163(n+1). A(2n+1,n) gives A092552(n+1). A(n,floor(n/2)) gives A306267. A(n+2,n) gives A001564. Cf. A130152. Sequence in context: A096670 A130461 A225631 * A267482 A130777 A187660 Adjacent sequences: A306206 A306207 A306208 * A306210 A306211 A306212 KEYWORD nonn,tabl AUTHOR Alois P. Heinz, Jan 29 2019 STATUS approved

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Last modified April 25 09:25 EDT 2024. Contains 371967 sequences. (Running on oeis4.)