A049129 Revert transform of (3x^2 - 1)/(-1 - x + 2x^2 + x^3).

1, 1, 2, 6, 20, 72, 271, 1055, 4212, 17152, 70966, 297482, 1260715, 5392627, 23251149, 100947165, 440939300, 1936388032, 8544353718, 37863744762, 168438633954, 751927422662, 3367361700052, 15123922285632, 68107641527359