Ulam numbers k such that k/3 is also an Ulam number.

Terms

a(0) =3a(1) =6a(2) =18a(3) =48a(4) =114a(5) =414a(6) =546a(7) =627a(8) =927a(9) =1023a(10) =1836a(11) =3090a(12) =4167a(13) =7539a(14) =7752a(15) =7884a(16) =7950a(17) =8250a(18) =9093a(19) =9621a(20) =9870a(21) =10779a(22) =11226a(23) =11622a(24) =11886a(25) =12363a(26) =12465a(27) =14994a(28) =16152a(29) =17391