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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 66 |
| 4 | 920 |
| 5 | 6350 |
| 6 | 29505 |
| 7 | 106036 |
| 8 | 317856 |
| 9 | 832140 |
| 10 | 1961025 |
| 11 | 4248310 |
| 12 | 8590296 |
| 13 | 16398746 |
| 14 | 29814785 |
| 15 | 51983400 |
| 16 | 87399040 |
| 17 | 142333656 |
| 18 | 225359361 |
| 19 | 347978730 |
| 20 | 525376600 |
| 21 | 777308070 |
| 22 | 1129138241 |
| 23 | 1613050076 |
| 24 | 2269437600 |
[0,1,66,920,6350,29505,106036,317856,832140, 1961025,4248310,8590296,16398746,29814785, 51983400,87399040,142333656,225359361,347978730, 525376600,777308070,1129138241,1613050076, 2269437600] |