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 A204541 #13 Mar 30 2012 17:31:31 %S A204541 4,14,15,21,22,35,38,55,57,74,87,95,119,143,145,166,187,205,215,217, %T A204541 247,253,254,259,278,287,289,291,305,314,335,339,341,394,403,407,427, %U A204541 471,493,505,514,515,517,538,553,559,565,589,614,622,623,629,633,634,649 %N A204541 Semiprimes with semiprime "look and say" descriptions. %C A204541 Semiprime analogous to A056815. %e A204541 14 is in the sequence because 14 is a semiprime (2*7) and its "Look and Say", 1114 is also a semiprime (2*557). %t A204541 LookAndSayA[n_] := FromDigits@ Flatten@ IntegerDigits@ Flatten[ Through[ {Length, First}[#]] & /@ Split@ IntegerDigits@ n]; semiPrimeQ[n_] := Plus @@ Last /@ FactorInteger@ n == 2; Select[ Range@ 650, semiPrimeQ@# && semiPrimeQ@ LookAndSayA@# &] %Y A204541 Cf. A001358, A056815. %K A204541 easy,nonn %O A204541 1,1 %A A204541 _Robert G. Wilson v_, Jan 27 2012