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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 26 |
| 4 | 142 |
| 5 | 946 |
| 6 | 7446 |
| 7 | 67658 |
| 8 | 697118 |
| 9 | 8031586 |
| 10 | 102312486 |
| 11 | 1427905658 |
| 12 | 21666671534 |
| 13 | 355138949394 |
| 14 | 6253348428598 |
| 15 | 117720540700842 |
| 16 | 2359368991571518 |
| 17 | 50157679523340994 |
| 18 | 1127327559500923974 |
| 19 | 26709016625807923418 |
| 20 | 665292778385210384078 |
[1,2,6,26,142,946,7446,67658,697118,8031586, 102312486,1427905658,21666671534,355138949394, 6253348428598,117720540700842,2359368991571518, 50157679523340994,1127327559500923974, 26709016625807923418,665292778385210384078] |