Positions of even numbers in A000408.

Terms

a(0) =2a(1) =5a(2) =6a(3) =8a(4) =11a(5) =12a(6) =13a(7) =16a(8) =18a(9) =20a(10) =21a(11) =23a(12) =25a(13) =27a(14) =28a(15) =30a(16) =33a(17) =34a(18) =38a(19) =40a(20) =42a(21) =44a(22) =45a(23) =47a(24) =49a(25) =51a(26) =53a(27) =55a(28) =56a(29) =57