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 A102782 #9 Oct 02 2013 15:47:24
%S A102782 111,1111,11111,1111111,11111111111,11111111111111111,
%T A102782 11111111111111111111111111111111111111111111111,
%U A102782 11111111111111111111111111111111111111111111111111111111111
%N A102782 Repunit semiprimes.
%F A102782 a(n) = A000042(A046413(n-1)). - _Ray Chandler_, Sep 06 2005
%e A102782 a(2)=1111 because 1111=11*101, so 1111 is semiprime as well as a repunit number.
%t A102782 Select[Table[FromDigits[PadRight[{},n,1]],{n,60}],PrimeOmega[#]==2&] (* _Harvey P. Dale_, Aug 28 2013 *)
%Y A102782 Cf. A046413 the repunit of length n has exactly 2 prime factors.
%K A102782 base,nonn
%O A102782 1,1
%A A102782 _Shyam Sunder Gupta_, Feb 11 2005