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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 8 |
| 3 | 61 |
| 4 | 464 |
| 5 | 3529 |
| 6 | 26840 |
| 7 | 204133 |
| 8 | 1552544 |
| 9 | 11807953 |
| 10 | 89805992 |
| 11 | 683024077 |
| 12 | 5194774640 |
| 13 | 39509124889 |
| 14 | 300488675192 |
| 15 | 2285382026869 |
| 16 | 17381590189376 |
| 17 | 132196575434401 |
| 18 | 1005427832907080 |
| 19 | 7646832936953437 |
| 20 | 58158379996906256 |
| 21 | 442326541164389737 |
[0,1,8,61,464,3529,26840,204133,1552544,11807953, 89805992,683024077,5194774640,39509124889, 300488675192,2285382026869,17381590189376, 132196575434401,1005427832907080,7646832936953437, 58158379996906256,442326541164389737] |