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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 2 |
| 6 | 15 |
| 7 | 102 |
| 8 | 854 |
| 9 | 7852 |
| 10 | 79867 |
| 11 | 890348 |
| 12 | 10799874 |
| 13 | 141647368 |
| 14 | 1997815108 |
| 15 | 30156348228 |
| 16 | 485117044074 |
| 17 | 8285798537070 |
| 18 | 149759338727585 |
| 19 | 2855791585334774 |
| 20 | 57300933786123530 |
| 21 | 1206811729692494152 |
| 22 | 26619251746350630597 |
| 23 | 613691499376088985144 |
[0,0,0,0,0,2,15,102,854,7852,79867,890348, 10799874,141647368,1997815108,30156348228, 485117044074,8285798537070,149759338727585, 2855791585334774,57300933786123530, 1206811729692494152,26619251746350630597, 613691499376088985144] |