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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 19 |
| 4 | 126 |
| 5 | 1080 |
| 6 | 10296 |
| 7 | 118440 |
| 8 | 1478304 |
| 9 | 21380544 |
| 10 | 351668736 |
| 11 | 6131649024 |
| 12 | 119107100160 |
| 13 | 2550758708736 |
| 14 | 57156393305088 |
| 15 | 1394626877005824 |
| 16 | 35414634429554688 |
| 17 | 969919192208203776 |
| 18 | 28498206264514043904 |
| 19 | 865692128959229214720 |
[1,4,19,126,1080,10296,118440,1478304,21380544, 351668736,6131649024,119107100160,2550758708736, 57156393305088,1394626877005824,35414634429554688, 969919192208203776,28498206264514043904, 865692128959229214720] |