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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 3 |
| 3 | 6 |
| 4 | 117 |
| 5 | 852 |
| 6 | 16335 |
| 7 | 231354 |
| 8 | 5169801 |
| 9 | 109149768 |
| 10 | 2929053339 |
| 11 | 81073827150 |
| 12 | 2593779841917 |
| 13 | 87970941597276 |
| 14 | 3298932148606887 |
| 15 | 131818125152516418 |
| 16 | 5692856683050644625 |
| 17 | 261303806858004143376 |
| 18 | 12794600152539073620531 |
| 19 | 662722202747157809616918 |
[1,0,3,6,117,852,16335,231354,5169801,109149768, 2929053339,81073827150,2593779841917, 87970941597276,3298932148606887, 131818125152516418,5692856683050644625, 261303806858004143376,12794600152539073620531, 662722202747157809616918] |