cp's OEIS Frontend

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).

%I A080998 #5 Mar 30 2012 17:27:18
%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.
%K A080998 nonn
%O A080998 1,2
%A A080998 _Matthew Vandermast_, Mar 02 2003