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 A180514 #12 Mar 30 2012 18:35:54
%S A180514 1,5,9,13,35,39,286,290,381,385,866,4376,10461,13506,19709,50925,
%T A180514 139046,144086,188517,623114,6815124,7226204,7647853,8970817,42716373,
%U A180514 64176516,189403472,240240118,463852538,520740373
%N A180514 Numbers starting with 1 such that the sum of any two distinct elements has an even number of distinct prime factors.
%C A180514 Numbers starting with 2 :
%C A180514 2, 4, 8, 10, 16, 18, 36, 199, 208, 1131, 1347, 3984, 5751, 7310, 27315, 129313, 134101, 169400, 589570,...
%C A180514 Numbers starting with 3 :
%C A180514 3, 7, 11, 15, 33, 41, 47, 65, 101, 203, 4102, 6392, 8507, 18608.
%e A180514 866 and 19709 are in the sequence because 19709 + 866 = 20575 = 5^2*823 has 2 prime factors.
%t A180514 t={1}; k=1; Do[k++; While[! And @@ EvenQ[Length /@ FactorInteger[t+k]], k++]; AppendTo[t, k], {18}]; t
%K A180514 nonn
%O A180514 1,2
%A A180514 _Michel Lagneau_, Jan 21 2011
%E A180514 a(20)-a(30) from _Donovan Johnson_, Jan 25 2011