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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 48 |
| 3 | 772 |
| 4 | 14256 |
| 5 | 285380 |
| 6 | 6023552 |
| 7 | 131991940 |
| 8 | 2974096544 |
| 9 | 68475379204 |
| 10 | 1603913377040 |
| 11 | 38099316926340 |
| 12 | 915619571011024 |
| 13 | 22222175033464260 |
| 14 | 543894269096547296 |
| 15 | 13409307961403740420 |
| 16 | 332707806061304185408 |
| 17 | 8301493488646359256580 |
[1,4,48,772,14256,285380,6023552,131991940, 2974096544,68475379204,1603913377040, 38099316926340,915619571011024,22222175033464260, 543894269096547296,13409307961403740420, 332707806061304185408,8301493488646359256580] |