Search: id:A087718
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%I A087718
%S A087718 4,6,9,15,25,35,49,77,91,121,143,169,187,209,221,247,289,299,323,361,
%T A087718 391,437,493,527,529,551,589,667,703,713,841,851,899,943,961,989,1073,
%U A087718 1147,1189,1247,1271,1333,1363,1369,1457,1517,1537,1591,1643,1681
%N A087718 Semiprimes with greater factor less than twice the smaller factor.
%C A087718 A084127(a(n)) < A084126(a(n))*2; subsequence of A001358; A001248 is a 
               subsequence.
%C A087718 Odd composite integers which do not have a representation as the sum 
               of an even number of consecutive integers. For instance, 27 is not 
               in the sequence because it has a representation as the sum of an 
               even number of consecutive integers (2+3+4+5+6+7). 35 is in the sequence 
               because it does not have such a representation. - Andrew Plewe (aplewe(AT)sbcglobal.net), 
               May 14 2007
%H A087718 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               Semiprime.html">Semiprime</a>
%e A087718 35=5*7 is a term, as 7<5*2=10;
%e A087718 21=3*7 is not a term, as 7>3*2=6.
%Y A087718 Sequence in context: A116589 A118688 A118691 this_sequence A033476 A118696 
               A065856
%Y A087718 Adjacent sequences: A087715 A087716 A087717 this_sequence A087719 A087720 
               A087721
%K A087718 nonn
%O A087718 1,1
%A A087718 Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Sep 29 2003

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