Search: id:A102401
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%I A102401
%S A102401 0,2,14,80,512,3776,31376,290456,2970296,33276536,405440216,5338909736,
%T A102401 75572075816,1144441325096,18464406889256,316212570391976,
%U A102401 5729159765566376
%N A102401 a(n) is the index of the permutation of order n having the least sum 
               of pairwise products as given by A026035.
%C A102401 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.
%e A102401 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:
%e A102401 6 2 4 3 5 1 7
%e A102401 and this is found at index 3776. Its products are
%e A102401 12 8 12 15 5 7
%e A102401 and sum is 59; a(7) of A026035 is 59. This allows us to give a(7) as 
               3776.
%Y A102401 Sequence in context: A121200 A112408 A026291 this_sequence A077461 A077444 
               A138126
%Y A102401 Adjacent sequences: A102398 A102399 A102400 this_sequence A102402 A102403 
               A102404
%K A102401 easy,nonn
%O A102401 2,2
%A A102401 Eugene McDonnell (eemcd(AT)mac.com), Feb 22 2005

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