Search: id:A131284
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%I A131284
%S A131284 5,80,86,613668
%N A131284 Numbers n such that difference between prime factors of n-th semiprime 
               is n.
%e A131284 sp(5)=14=2*7 and 7-2=5, sp(80)=249=3*83 and 83-3=80, sp(86)=267=3*89 
               and 89-3=86; sp(n)=nth semiprime.
%o A131284 (PARI/gp from M. F. Hasler)
%o A131284 { n=0; j=1; /* n=3068365-1; j=613668;*/
%o A131284 while( l=(j\10^4+1)*10^4, until( l < j++, until(bigomega(n+=1)==2,);
%o A131284 if(2!=#f=factor(n)[,1],next); if(j==f[2]-f[1],print("\n",[j,n,f])));
%o A131284 print1(j-1,":"n", "))}
%Y A131284 Cf. A084126, A084127, A109313, A064910.
%Y A131284 Sequence in context: A141828 A134531 A062250 this_sequence A105917 A144344 
               A062364
%Y A131284 Adjacent sequences: A131281 A131282 A131283 this_sequence A131285 A131286 
               A131287
%K A131284 more,nonn
%O A131284 1,1
%A A131284 Zak Seidov (zakseidov(AT)yahoo.com), Sep 25 2007
%E A131284 n=613668 (p=5, q=613673) from M. F. Hasler (maximilian.hasler(AT)gmail.com), 
               Sep 28 2007

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