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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 35 |
| 5 | 290 |
| 6 | 2680 |
| 7 | 26379 |
| 8 | 267598 |
| 9 | 2758016 |
| 10 | 28749456 |
| 11 | 302120154 |
| 12 | 3196299285 |
| 13 | 34007337629 |
[1,1,6,35,290,2680,26379,267598,2758016,28749456, 302120154,3196299285,34007337629] |