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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 74 |
| 5 | 274 |
| 6 | 1103 |
| 7 | 4346 |
| 8 | 18145 |
| 9 | 74331 |
| 10 | 318312 |
| 11 | 1336411 |
| 12 | 5827832 |
| 13 | 24909882 |
| 14 | 110034713 |
| 15 | 476834165 |
| 16 | 2127342959 |
| 17 | 9318014380 |
| 18 | 41903405413 |
| 19 | 185131893648 |
| 20 | 837932888864 |
| 21 | 3728559784111 |
| 22 | 16966589249858 |
| 23 | 75950246723095 |
| 24 | 347176536974470 |
| 25 | 1562080118187658 |
| 26 | 7168193213394010 |
| 27 | 32395087374479255 |
[1,2,6,20,74,274,1103,4346,18145,74331,318312, 1336411,5827832,24909882,110034713,476834165, 2127342959,9318014380,41903405413,185131893648, 837932888864,3728559784111,16966589249858, 75950246723095,347176536974470,1562080118187658, 7168193213394010,32395087374479255] |