A102401 - OEIS

A102401

a(n) is the index of the permutation of order n having the least sum of pairwise products as given by A026035.

0, 2, 14, 80, 512, 3776, 31376, 290456, 2970296, 33276536, 405440216, 5338909736, 75572075816, 1144441325096, 18464406889256, 316212570391976, 5729159765566376

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OFFSET

2,2

COMMENTS

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.

LINKS

Table of n, a(n) for n=2..18.

EXAMPLE

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.

CROSSREFS

Sequence in context: A220867 A216985 A361813 * A077461 A077444 A335693

Adjacent sequences: A102398 A102399 A102400 * A102402 A102403 A102404

KEYWORD

easy,nonn

AUTHOR

Eugene McDonnell (eemcd(AT)mac.com), Feb 22 2005

STATUS

approved