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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 28 |
| 5 | 262 |
| 6 | 3428 |
| 7 | 52289 |
| 8 | 1147221 |
| 9 | 30161625 |
| 10 | 893291633 |
| 11 | 30894822277 |
| 12 | 1214415301634 |
| 13 | 52617692115135 |
| 14 | 2528123847871538 |
| 15 | 133088227043557512 |
| 16 | 7574733515354756765 |
| 17 | 466116310963215784930 |
| 18 | 30810712157925101729430 |
| 19 | 2173319693639115252360852 |
| 20 | 163247410881483617710298406 |
[1,1,2,7,28,262,3428,52289,1147221,30161625, 893291633,30894822277,1214415301634, 52617692115135,2528123847871538, 133088227043557512,7574733515354756765, 466116310963215784930,30810712157925101729430, 2173319693639115252360852, 163247410881483617710298406] |