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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 6 |
| 3 | 12 |
| 4 | 30 |
| 5 | 60 |
| 6 | 138 |
| 7 | 252 |
| 8 | 600 |
| 9 | 1008 |
| 10 | 2490 |
| 11 | 4092 |
| 12 | 10050 |
| 13 | 16380 |
| 14 | 40698 |
| 15 | 65460 |
| 16 | 163200 |
| 17 | 262140 |
| 18 | 654192 |
| 19 | 1048572 |
| 20 | 2618850 |
| 21 | 4194036 |
| 22 | 10481658 |
| 23 | 16777212 |
| 24 | 41932200 |
| 25 | 67108800 |
| 26 | 167755770 |
| 27 | 268434432 |
| 28 | 671047650 |
[4,6,12,30,60,138,252,600,1008,2490,4092,10050, 16380,40698,65460,163200,262140,654192,1048572, 2618850,4194036,10481658,16777212,41932200, 67108800,167755770,268434432,671047650] |