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 A287612 #14 May 31 2017 22:57:10 %S A287612 1,2,4,18,114,131,180,258,324,412,431,605,646,864,1037,1081,1101,1167, %T A287612 1296,1313,1404,1470,1765,1856,1858,1900,1944,2032,2117,2327,2572, %U A287612 2630,2635,2674,2787,2809,2814,2897,3068,3214,3219,3261,3393,3451,3591,3622,3630 %N A287612 Ulam numbers k such that 4*k is also an Ulam number. %t A287612 (* First run one of the programs for A002858 to populate the ulams list *) A287612 = ulams; curr = 1; While[curr < Length[ulams] + 1, A287612[[curr]] = ulams[[curr]] * Boole[MemberQ[ulams, 4ulams[[curr]]]]; curr++]; DeleteCases[A287612, 0] (* _Alonso del Arte_, May 28 2017 *) %Y A287612 Cf. A002858, A068791, A285885. %K A287612 nonn %O A287612 1,2 %A A287612 _Enrique Navarrete_, May 27 2017