A081852 Consider recurrence b(0) = n/3, b(n) = b(0)*ceiling(b(n-1)); sequence gives first integer reached (or -1 if no integer is ever reached).

1, 4, 20, 2, 7, 8, 3, 26631380, 55, 4, 416, 112, 5, 32, 34, 6, 285, 13960, 7, 67358874, 214544, 8, 75, 78, 9, 62186796, 7399041846, 10, 1178, 173857344, 11, 136, 140, 12, 24494, 2090, 13, 78824360, 2624, 14, 215, 220, 15, 3772, 61617, 16, 23001295794169, 78900, 17, 312