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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 2 |
| 3 | 9 |
| 4 | 36 |
| 5 | 165 |
| 6 | 918 |
| 7 | 6111 |
| 8 | 47304 |
| 9 | 416097 |
| 10 | 4091130 |
| 11 | 44417043 |
| 12 | 527456556 |
| 13 | 6798432069 |
| 14 | 94499679582 |
| 15 | 1408924024695 |
| 16 | 22425642181008 |
| 17 | 379514672913321 |
| 18 | 6804212771165634 |
| 19 | 128827325000617947 |
| 20 | 2568509718703606260 |
| 21 | 53787877376348226573 |
| 22 | 1180349932648067726886 |
[0,0,2,9,36,165,918,6111,47304,416097,4091130, 44417043,527456556,6798432069,94499679582, 1408924024695,22425642181008,379514672913321, 6804212771165634,128827325000617947, 2568509718703606260,53787877376348226573, 1180349932648067726886] |