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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 9 |
| 5 | 44 |
| 6 | 265 |
| 7 | 1854 |
| 8 | 14833 |
| 9 | 101976 |
| 10 | 619009 |
| 11 | 3449752 |
| 12 | 18376224 |
| 13 | 96559908 |
| 14 | 511111965 |
| 15 | 2761247612 |
| 16 | 15348014345 |
| 17 | 86603917480 |
| 18 | 491567055577 |
| 19 | 2789697424330 |
| 20 | 15773859067112 |
| 21 | 88743605142976 |
| 22 | 496953313619236 |
| 23 | 2774429422110882 |
| 24 | 15478834487896593 |
[1,0,1,2,9,44,265,1854,14833,101976,619009, 3449752,18376224,96559908,511111965,2761247612, 15348014345,86603917480,491567055577, 2789697424330,15773859067112,88743605142976, 496953313619236,2774429422110882, 15478834487896593] |