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| n | a(n) |
|---|---|
| 2 | 5 |
| 3 | 18 |
| 4 | 110 |
| 5 | 508 |
| 6 | 4968 |
| 7 | 25824 |
| 8 | 305376 |
| 9 | 2375616 |
| 10 | 28316832 |
| 11 | 202354752 |
| 12 | 4771240704 |
| 13 | 33499830528 |
| 14 | 612464852736 |
| 15 | 9023719675392 |
| 16 | 176001733301760 |
| 17 | 1649576855476224 |
| 18 | 56693983168309248 |
| 19 | 551579829498390528 |
| 20 | 20888523161929138176 |
| 21 | 342595860998544285696 |
[5,18,110,508,4968,25824,305376,2375616,28316832, 202354752,4771240704,33499830528,612464852736, 9023719675392,176001733301760,1649576855476224, 56693983168309248,551579829498390528, 20888523161929138176,342595860998544285696] |