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A179620 a(n) = largest k such that A002808(n+1) = A002808(n) + (A002808(n) mod k), or 0 if no such k exists.

%I A179620 #9 Mar 30 2012 17:25:56
%S A179620 0,4,7,8,8,10,13,14,14,16,19,20,20,23,24,25,26,26,28,31,32,33,34,34,
%T A179620 37,38,38,40,43,44,44,47,48,49,50,50,53,54,55,56,56,58,61,62,63,64,64,
%U A179620 67,68,68,70,73,74,75,76,76,79,80,80,83,84,85,86,86,89
%N A179620 a(n) = largest k such that A002808(n+1) = A002808(n) + (A002808(n) mod k), or 0 if no such k exists.
%C A179620 a(n) = A002808(n) - A073783(n) if A002808(n) - A073783(n) > A073783(n), 0 otherwise.
%C A179620 A002808(n): composite numbers; A073783(n): first difference of composite numbers.
%H A179620 Rémi Eismann, <a href="/A179620/b179620.txt">Table of n, a(n) for n = 1..10000</a>
%e A179620 For n = 1 we have A002808(n) = 4, A002808(n+1) = 6; there is no k such that 6 - 4 = 2 = (4 mod k), hence a(1) = 0.
%e A179620 For n = 3 we have A002808(n) = 8, A002808(n+1) = 9; 7 is the largest k such that 9 - 8 = 1 = (8 mod k), hence a(3) = 7; a(3) = A002808(3) - A073783(3) = 8 - 1 = 7.
%e A179620 For n = 24 we have A002808(n) = 36, A002808(n+1) = 38; 34 is the largest k such that 38 - 36 = 2 = (36 mod k), hence a(24) = 34; a(24) = A002808(24) - A073783(24) = 34.
%Y A179620 Cf. A002808, A073783, A130882, A179621, A118534, A117078, A117563, A001223.
%K A179620 nonn,easy
%O A179620 1,2
%A A179620 _Rémi Eismann_, Jan 09 2011