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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 61 |
| 4 | 516 |
| 5 | 4621 |
| 6 | 40626 |
| 7 | 359281 |
| 8 | 3171336 |
| 9 | 28010041 |
| 10 | 247343646 |
| 11 | 2184312901 |
| 12 | 19289468556 |
| 13 | 170344633861 |
| 14 | 1504304517066 |
| 15 | 13284442948921 |
| 16 | 117314270620176 |
| 17 | 1035996697444081 |
| 18 | 9148836950168886 |
| 19 | 80792939137115341 |
| 20 | 713478558576914196 |
[1,1,6,61,516,4621,40626,359281,3171336,28010041, 247343646,2184312901,19289468556,170344633861, 1504304517066,13284442948921,117314270620176, 1035996697444081,9148836950168886, 80792939137115341,713478558576914196] |