Search: id:A080998
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%I A080998
%S A080998 1,2,3,4,6,5,10,7,11,9,18,8,20,13,12,15,25,14,33,16,21,23,40,17,32,28,
%T A080998 27,22,53,19,56,30,35,39,36,24,69,46,43,26,79,29,89,38,37,55,95,31,67,
%U A080998 45,57,47,108,41,60,42,65,75
%N A080998 a(n) is n's rank among the positive integers in terms of centrality -the 
               fraction of n represented by the average gcd of n and the positive 
               integers, or A018804(n)/n^2 (cf. A080997).
%e A080998 a(5)=6 because the centrality of 5 is 9/25 (.36), which places it sixth 
               among positive integers in centrality; it ranks behind 1 (whose centrality 
               is 1), 2 (3/4, .75), 3 (5/9, .555...), 4 (1/2, .5) and 6 (5/12, .41666...).
%Y A080998 A080997 gives fuller description of centrality, as well as finite portion 
               of the arrangement of positive integers in order of their centrality. 
               For more about where numbers occur in A080997, see also A081000, 
               A081001, A081028, A081029.
%Y A080998 Sequence in context: A075159 A095424 A064275 this_sequence A119629 A014631 
               A064787
%Y A080998 Adjacent sequences: A080995 A080996 A080997 this_sequence A080999 A081000 
               A081001
%K A080998 nonn
%O A080998 1,2
%A A080998 Matthew Vandermast (ghodges14(AT)comcast.net), Mar 02 2003

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