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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 54 |
| 5 | 184 |
| 6 | 868 |
| 7 | 3270 |
| 8 | 15797 |
| 9 | 62573 |
| 10 | 306060 |
| 11 | 1252011 |
| 12 | 6168402 |
| 13 | 25808068 |
| 14 | 127724851 |
| 15 | 543318743 |
| 16 | 2696792155 |
| 17 | 11618463835 |
| 18 | 57783118598 |
| 19 | 251466517576 |
| 20 | 1252361879418 |
| 21 | 5495032545579 |
| 22 | 27393340026109 |
| 23 | 121016104496380 |
| 24 | 603706939462674 |
| 25 | 2682399778543295 |
| 26 | 13388555204024655 |
| 27 | 59782410913675045 |
[1,1,4,12,54,184,868,3270,15797,62573,306060, 1252011,6168402,25808068,127724851,543318743, 2696792155,11618463835,57783118598,251466517576, 1252361879418,5495032545579,27393340026109, 121016104496380,603706939462674,2682399778543295, 13388555204024655,59782410913675045] |