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 A188495 Number of permutations p on the set [n] with the properties that abs(p(i)-i) <= 3 for all i, p(1) <= 2, and p(4) >= 2. 6
 0, 1, 2, 4, 10, 36, 120, 368, 1089, 3304, 10168, 31312, 95880, 293120, 896824, 2746569, 8411818, 25756220, 78853410, 241421436, 739183568, 2263249600, 6929580817, 21216729488, 64960656448, 198894856144, 608971496032, 1864533223584, 5708777321872 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS a(n) is also the permanent of the n-by-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 zeroes in the (3,1) and (4,1)-entries), and is zero elsewhere. This is row 10 of Klove's Table 3. LINKS Nathaniel Johnston, Table of n, a(n) for n = 0..119 Torleiv Klove, 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. FORMULA Contribution from Nathaniel Johnston, Apr 10 2011 (Start): a(n) = A188493(n+1) - A188491(n) - A188497(n). a(n) = A002526(n-1) + A188494(n-1). (End) MAPLE with (LinearAlgebra): A188495:= n-> `if` (n=0, 0, Permanent (Matrix (n, (i, j)->               `if` (abs(j-i)<4 and [i, j]<>[3, 1] and [i, j]<>[4, 1] and [i, j]<>[1, 4], 1, 0)))): seq (A188495(n), n=0..20); CROSSREFS Sequence in context: A125859 A103854 A126941 * A038077 A006396 A192502 Adjacent sequences:  A188492 A188493 A188494 * A188496 A188497 A188498 KEYWORD nonn AUTHOR N. J. A. Sloane, Apr 01 2011 EXTENSIONS Name and comments edited, and a(12) - a(28) from Nathaniel Johnston, Apr 10 2011 STATUS approved

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Last modified June 19 11:55 EDT 2013. Contains 226404 sequences.