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Search: id:A079340
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| A079340 |
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Absolute value of determinant of n X n matrix whose entries are the integers from 1 to n^2 spiraling outward, ending in a corner. |
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+0
4
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| 1, 5, 72, 1380, 31920, 861840, 26611200, 925404480, 35805369600, 1526139014400, 71066912716800, 3590219977344000, 195589552648089600, 11430978821982720000, 713448513897799680000, 47363888351558338560000
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Ending in the NW or SE corner and n is even OR ending in the NE or SW corner and n is odd then the sign is positive, otherwise it is negative.
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FORMULA
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Conjecture: a(n) = (2n^2-3n+3) (2n-2)!/(2 (n-1)!). - Dean Hickerson (dean.hickerson(AT)yahoo.com), Jan 30 2003
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EXAMPLE
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n=2, det=-5: {1 2 / 4 3 }.
n=3, det=72: {7 8 9 / 6 1 2 / 5 4 3 }.
n=4, det=-1380: { 7 8 9 10 / 6 1 2 11 /5 4 3 12 / 16 15 14 13 }.
n=5, det=31920: { 21 22 23 24 25 / 20 7 8 9 10 / 19 6 1 2 11 /18 5 4 3 12 / 17 16 15 14 13 }
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CROSSREFS
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Cf. A078475, A023999, A067276, A052182.
Sequence in context: A120808 A092204 A079874 this_sequence A136637 A138623 A070526
Adjacent sequences: A079337 A079338 A079339 this_sequence A079341 A079342 A079343
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KEYWORD
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nonn
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AUTHOR
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Kit Vongmahadlek (kit119(AT)yahoo.com), Jan 03 2003
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EXTENSIONS
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Extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 25 2003
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