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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 6 |
| 4 | 23 |
| 5 | 112 |
| 6 | 561 |
| 7 | 3519 |
| 8 | 39132 |
| 9 | 437312 |
| 10 | 4828352 |
| 11 | 70006528 |
| 12 | 1118710784 |
| 13 | 17726058496 |
| 14 | 298648682496 |
| 15 | 7527505969152 |
[1,3,6,23,112,561,3519,39132,437312,4828352, 70006528,1118710784,17726058496,298648682496, 7527505969152] |