A287612 Ulam numbers k such that 4*k is also an Ulam number.

1, 2, 4, 18, 114, 131, 180, 258, 324, 412, 431, 605, 646, 864, 1037, 1081, 1101, 1167, 1296, 1313, 1404, 1470, 1765, 1856, 1858, 1900, 1944, 2032, 2117, 2327, 2572, 2630, 2635, 2674, 2787, 2809, 2814, 2897, 3068, 3214, 3219, 3261, 3393, 3451, 3591, 3622, 3630

Offset: 1

Author

Enrique Navarrete, May 27 2017

Keywords

• nonn

Crossrefs

Cf. A002858, A068791, A285885.

Programs

Mathematica

(* 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 *)