A046338 Palindromes with an even number of prime factors (counted with multiplicity).

4, 6, 9, 22, 33, 55, 77, 88, 111, 121, 141, 161, 202, 232, 262, 303, 323, 393, 414, 424, 444, 454, 484, 505, 515, 525, 535, 545, 565, 585, 626, 636, 666, 676, 686, 707, 717, 737, 767, 808, 818, 838, 858, 868, 878, 898, 939, 949, 959, 979, 989, 999, 1111, 1441