$n = 250_000_000_000;

$a = 2.5;

while ($n>2) {
  print "$n\n";
  $n /= $a;
}

^D
250000000000
100000000000
40000000000
16000000000
6400000000
2560000000
1024000000
409600000
163840000
65536000
26214400
10485760
4194304
1677721.6
671088.64
268435.456
107374.1824
42949.67296
17179.869184
6871.9476736
2748.77906944
1099.511627776
439.8046511104
175.92186044416
70.368744177664
28.1474976710656
11.2589990684262
4.5035996273705