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Search: id:A102401
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| A102401 |
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a(n) is the index of the permutation of order n having the least sum of pairwise products as given by A026035. |
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+0
1
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| 0, 2, 14, 80, 512, 3776, 31376, 290456, 2970296, 33276536, 405440216, 5338909736, 75572075816, 1144441325096, 18464406889256, 316212570391976, 5729159765566376
(list; graph; listen)
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OFFSET
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2,2
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COMMENT
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A026035 gives the minimum sum of products for permutations and was used to validate the results above. There is a companion index for the permutations that are the reversals of those indexed here. A formula would be very welcome.
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EXAMPLE
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In the permutation table of order 7 the first instance of a row having the least sum of overlapping pairwise products can be found empirically to be:
6 2 4 3 5 1 7
and this is found at index 3776. Its products are
12 8 12 15 5 7
and sum is 59; a(7) of A026035 is 59. This allows us to give a(7) as 3776.
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CROSSREFS
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Sequence in context: A121200 A112408 A026291 this_sequence A077461 A077444 A138126
Adjacent sequences: A102398 A102399 A102400 this_sequence A102402 A102403 A102404
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KEYWORD
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easy,nonn
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AUTHOR
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Eugene McDonnell (eemcd(AT)mac.com), Feb 22 2005
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