A064004 At step n in computing A064413, sequence gives smallest multiple of 2 not yet seen, divided by 2.

1, 2, 3, 4, 4, 4, 4, 5, 7, 7, 7, 7, 8, 8, 8, 8, 10, 11, 13, 13, 13, 13, 13, 13, 13, 13, 16, 16, 16, 16, 17, 19, 19, 19, 19, 20, 20, 20, 20, 22, 23, 24, 24, 24, 25, 26, 27, 28, 29, 29, 29, 29, 29, 29, 29, 31, 31, 31, 31, 32, 32, 32, 32, 34, 37, 38, 38, 38, 38, 38, 40