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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 8 |
| 4 | 23 |
| 5 | 72 |
| 6 | 279 |
| 7 | 1236 |
| 8 | 6313 |
| 9 | 36133 |
| 10 | 230119 |
| 11 | 1611138 |
| 12 | 12308693 |
| 13 | 101865629 |
| 14 | 907900133 |
| 15 | 8669791288 |
| 16 | 88309821406 |
| 17 | 955736037556 |
| 18 | 10951928988000 |
| 19 | 132472073263683 |
| 20 | 1686686835102650 |
| 21 | 22549341913109430 |
| 22 | 315817852408881670 |
[0,1,3,8,23,72,279,1236,6313,36133,230119,1611138, 12308693,101865629,907900133,8669791288, 88309821406,955736037556,10951928988000, 132472073263683,1686686835102650, 22549341913109430,315817852408881670] |