A018103 Powers of fourth root of 20 rounded to nearest integer.

1, 2, 4, 9, 20, 42, 89, 189, 400, 846, 1789, 3783, 8000, 16918, 35777, 75659, 160000, 338359, 715542, 1513187, 3200000, 6767176, 14310835, 30263731, 64000000, 135343522, 286216701, 605274630, 1280000000