OFFSET
0,3
COMMENTS
For n >= 2, a(n) is the number of permutations p on the set [n] with the properties that abs(p(i)-i) <= 3 for all i, p(j) <= 1+j for j=1,2, and p(4) >= 2.
For n >= 2, a(n) is also the permanent of the n X n matrix that has ones on its diagonal, ones on its three superdiagonals (with the exception of a zero in the (1,4)-entry), ones on its three subdiagonals (with the exception of zeros in the (3,1), (4,1), (4,2), and (5,2)-entries), and is zero elsewhere.
This is row 12 of Kløve's Table 3.
LINKS
Colin Barker, Table of n, a(n) for n = 0..1000
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.
Index entries for linear recurrences with constant coefficients, signature (2,2,0,10,8,-2,-16,-10,-2,4,2,0,2,1).
FORMULA
G.f.: -x^2*(x^9 +2*x^8 -2*x^4 -2*x^3 -5*x^2 +2) / ((x -1)*(x^13 +3*x^12 +3*x^11 +5*x^10 +9*x^9 +7*x^8 -3*x^7 -19*x^6 -21*x^5 -13*x^4 -3*x^3 -3*x^2 -x +1)). - Colin Barker, Dec 13 2014
MAPLE
MATHEMATICA
a[n_] := Permanent[Table[If[Abs[j - i] < 4 && {i, j} != {1, 4} && {i, j} != {3, 1} && {i, j} != {4, 1} && {i, j} != {4, 2} && {i, j} != {5, 2}, 1, 0], {i, 1, n}, {j, 1, n}]]; a[1] = 0; Table[an = a[n]; Print["a(", n, ") = ", an]; an, {n, 0, 20}](* Jean-François Alcover, Jan 07 2016, adapted from Maple *)
CoefficientList[Series[x^2 (x^9 + 2 x^8 - 2 x^4 - 2 x^3 - 5 x^2 + 2) / ((1 - x) (x^13 + 3 x^12 + 3 x^11 + 5 x^10 + 9 x^9 + 7 x^8 - 3 x^7 - 19 x^6 - 21 x^5 - 13 x^4 - 3 x^3 - 3 x^2 - x + 1)), {x, 0, 33}], x] (* Vincenzo Librandi, Jan 07 2016 *)
PROG
(PARI) concat([0, 0], Vec(-x^2*(x^9 +2*x^8 -2*x^4 -2*x^3 -5*x^2 +2) / ((x -1)*(x^13 +3*x^12 +3*x^11 +5*x^10 +9*x^9 +7*x^8 -3*x^7 -19*x^6 -21*x^5 -13*x^4 -3*x^3 -3*x^2 -x +1)) + O(x^100))) \\ Colin Barker, Dec 13 2014
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Apr 01 2011
EXTENSIONS
Name and comments edited, and a(12)-a(28) from Nathaniel Johnston, Apr 11 2011
STATUS
approved