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

Terms

a(0) =2a(1) =4a(2) =6a(3) =8a(4) =16a(5) =26a(6) =36a(7) =72a(8) =106a(9) =114a(10) =138a(11) =412a(12) =546a(13) =800a(14) =1966a(15) =2616a(16) =5162a(17) =6410a(18) =8236a(19) =27062a(20) =29784a(21) =177104a(22) =278256a(23) =342486a(24) =556126a(25) =664364a(26) =1388708a(27) =6833546a(28) =8622762a(29) =9734048