Ulam numbers such that 2*n is also an Ulam number.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =8a(5) =13a(6) =18a(7) =36a(8) =53a(9) =57a(10) =69a(11) =206a(12) =273a(13) =400a(14) =983a(15) =1308a(16) =2581a(17) =3205a(18) =4118a(19) =13531a(20) =14892a(21) =88552a(22) =139128a(23) =171243a(24) =278063a(25) =332182a(26) =694354a(27) =3416773a(28) =4311381a(29) =4867024