This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A131284 #17 Dec 21 2015 12:53:10
%S A131284 5,80,86,613668,6384425704
%N A131284 Numbers n such that difference between prime factors of n-th semiprime is n.
%C A131284 The 6384425704th semiprime is 44690979977 = 7*6384425711. 6384425711 - 7 = 6384425704. - _Donovan Johnson_, Jul 11 2010
%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) = n-th semiprime.
%o A131284 (PARI)
%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", "))} \\ _M. F. Hasler_, Sep 28 2007
%Y A131284 Cf. A064910, A084126, A084127, A109313.
%K A131284 more,nonn
%O A131284 1,1
%A A131284 _Zak Seidov_, Sep 25 2007
%E A131284 a(4) = 613668 (p=5, q=613673) from _M. F. Hasler_, Sep 28 2007
%E A131284 a(5) from _Donovan Johnson_, Jul 11 2010