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 A242832 #16 Jun 02 2014 22:49:16
%S A242832 6,14,15,62,254,511,2047,16382,262142,1048574,8388607,4294967294,
%T A242832 137438953471,562949953421311,576460752303423487,4611686018427387902,
%U A242832 147573952589676412927,9671406556917033397649407,1237940039285380274899124222,158456325028528675187087900671
%N A242832 Semiprimes of the form 2^k - 1 or 2^k - 2.
%C A242832 Union of A092561 and 2*A000668.
%t A242832 Select[Flatten[Table[{2^k - 2, 2^k - 1}, {k, 100}]], PrimeOmega[#] == 2 &] (* _Alonso del Arte_, May 26 2014 *)
%Y A242832 Cf. A092561, A000668.
%K A242832 nonn
%O A242832 1,1
%A A242832 _Juri-Stepan Gerasimov_, May 23 2014
%E A242832 More terms from _Alonso del Arte_, May 26 2014