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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 23 |
| 5 | 106 |
| 6 | 558 |
| 7 | 3284 |
| 8 | 21200 |
| 9 | 148539 |
| 10 | 1119273 |
| 11 | 9013112 |
| 12 | 77106652 |
| 13 | 697811164 |
| 14 | 6652604804 |
| 15 | 66593158893 |
| 16 | 697756930786 |
| 17 | 7633155361594 |
| 18 | 86969814549075 |
| 19 | 1029939820075074 |
| 20 | 12652809025029242 |
| 21 | 160977119684852369 |
| 22 | 2117642963178349336 |
| 23 | 28763717105362639324 |
[1,1,2,6,23,106,558,3284,21200,148539,1119273, 9013112,77106652,697811164,6652604804,66593158893, 697756930786,7633155361594,86969814549075, 1029939820075074,12652809025029242, 160977119684852369,2117642963178349336, 28763717105362639324] |