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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 6 |
| 5 | 36 |
| 6 | 180 |
| 7 | 1008 |
| 8 | 6048 |
| 9 | 34272 |
| 10 | 180662 |
| 11 | 940896 |
| 12 | 5018112 |
| 13 | 27433728 |
| 14 | 152845056 |
| 15 | 862725426 |
| 16 | 4895520768 |
| 17 | 27770211072 |
| 18 | 157364529408 |
| 19 | 892662156288 |
| 20 | 5078255822436 |
| 21 | 28990266218496 |
| 22 | 166029537715200 |
| 23 | 953309368018944 |
| 24 | 5484206701412352 |
| 25 | 31596861676172076 |
[0,0,0,6,36,180,1008,6048,34272,180662,940896, 5018112,27433728,152845056,862725426,4895520768, 27770211072,157364529408,892662156288, 5078255822436,28990266218496,166029537715200, 953309368018944,5484206701412352, 31596861676172076] |