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 A197640 #16 May 13 2013 01:49:58 %S A197640 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26, %T A197640 27,28,30,32,33,34,35,36,38,39,40,42,44,45,46,48,50,51,52,54,56,58,60, %U A197640 62,63,64,66,70,72,75,78,80,82,84,88,90,96,100,102,105,108,110,114,120,126,130,132,138,140,144,150,156,168,180,190,204,210,240,270,330,420 %N A197640 Numbers not representable as the sum of two coprime, squarefree, composite, positive integers. %C A197640 a(87) = 420 is probably the last term. %o A197640 (PARI) is(n)=for(k=6,n\2,if(gcd(k,n-k)==1&&!isprime(k)&&!isprime(n-k)&&issquarefree(k)&&issquarefree(n-k),return(0)));1 \\ _Charles R Greathouse IV_, Oct 18 2011 %Y A197640 Cf. A197629, A096076. %K A197640 nonn %O A197640 1,2 %A A197640 _Jason Holland_, Oct 16 2011