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 A068791 #17 May 14 2017 17:07:26 %S A068791 1,2,3,4,8,13,18,36,53,57,69,206,273,400,983,1308,2581,3205,4118, %T A068791 13531,14892,88552,139128,171243,278063,332182,694354,3416773,4311381, %U A068791 4867024 %N A068791 Ulam numbers such that 2*n is also an Ulam number. %Y A068791 Cf. A002858, A068799. %K A068791 more,nonn %O A068791 1,2 %A A068791 _Naohiro Nomoto_, Mar 29 2002 %E A068791 More terms from _Jud McCranie_, Feb 12 2003