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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 81 |
| 6 | 332 |
| 7 | 1420 |
| 8 | 6266 |
| 9 | 28318 |
| 10 | 130412 |
| 11 | 609808 |
| 12 | 2887582 |
| 13 | 13818590 |
| 14 | 66726628 |
| 15 | 324713196 |
| 16 | 1590853485 |
| 17 | 7840315329 |
| 18 | 38843186366 |
| 19 | 193342353214 |
| 20 | 966409013021 |
| 21 | 4848846341569 |
| 22 | 24412146213116 |
| 23 | 123290812268404 |
| 24 | 624448756434476 |
| 25 | 3171046361310556 |
[1,1,2,6,21,81,332,1420,6266,28318,130412,609808, 2887582,13818590,66726628,324713196,1590853485, 7840315329,38843186366,193342353214,966409013021, 4848846341569,24412146213116,123290812268404, 624448756434476,3171046361310556] |