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 A026506 #5 Mar 31 2012 13:50:34 %S A026506 1,3,4,5,6,8,10,12,14,16,18,20,22,26,28,30,31,32,36,38,42,46,49,50,52, %T A026506 58,60,66,70,71,78,86,87,88,97,100,102,103,106,109,119,122,130,135, %U A026506 136,139,148,149,150,151,153,158,163,167,169,172 %N A026506 a(n) = least positive integer > a(n-1) and not a(j)*a(k) + a(k)*a(i) + a(i)*a(j) for 1<=i<=j<=k<=n. %K A026506 nonn %O A026506 1,2 %A A026506 _Clark Kimberling_ %E A026506 More terms from _Naohiro Nomoto_, Sep 15 2001