%I #17 Dec 21 2015 12:53:10
%S 5,80,86,613668,6384425704
%N Numbers n such that difference between prime factors of n-th semiprime is n.
%C The 6384425704th semiprime is 44690979977 = 7*6384425711. 6384425711 - 7 = 6384425704. - _Donovan Johnson_, Jul 11 2010
%e 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) = n-th semiprime.
%o (PARI)
%o { n=0; j=1; /* n=3068365-1; j=613668;*/
%o while( l=(j\10^4+1)*10^4, until( l < j++, until(bigomega(n+=1)==2,);
%o if(2!=#f=factor(n)[,1],next); if(j==f[2]-f[1],print("\n",[j,n,f])));
%o print1(j-1,":"n", "))} \\ _M. F. Hasler_, Sep 28 2007
%Y Cf. A064910, A084126, A084127, A109313.
%K more,nonn
%O 1,1
%A _Zak Seidov_, Sep 25 2007
%E a(4) = 613668 (p=5, q=613673) from _M. F. Hasler_, Sep 28 2007
%E a(5) from _Donovan Johnson_, Jul 11 2010