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%I #6 Mar 31 2012 14:42:50
%S 0,0,2,6,13,9,2,19,2,19,2,3,4,37,8,43,47,47,53,2,6,59,61,8,71,6,79,2,
%T 5,83,89,2,3,12,101,107,4,3,3,2,11
%N a(n) = smallest k such that A001358(n+1) = A001358(n) + (A001358(n) mod k), or 0 if no such k exists.
%C a(n) is the "weight" of semiprimes.
%C The decomposition of semiprimes into weight * level + gap is A001358(n) = a(n) * A184729(n) + A065516(n) if a(n) > 0.
%H Remi Eismann, <a href="/A130533/b130533.txt">Table of n, a(n) for n=1..9999</a>
%e For n = 1 we have A001358(n) = 4, A001358(n+1) = 6; there is no k such that 6 - 4 = 2 = (4 mod k), hence a(1) = 0.
%e For n = 3 we have A001358(n) = 9, A001358(n+1) = 10; 2 is the smallest k such that 10 - 9 = 1 = (9 mod k), hence a(3) = 2.
%e For n = 19 we have A001358(n) = 55, A001358(n+1) = 57; 53 is the smallest k such that 57 - 55 = 2 = (55 mod k), hence a(19) = 53.
%Y Cf. A001358, A065516, A184729, A184728, A117078, A117563, A001223, A118534.
%K nonn
%O 1,3
%A _Rémi Eismann_, Aug 16 2007 - Jan 20 2011
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