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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 40 |
| 3 | 292 |
| 4 | 2308 |
| 5 | 19580 |
| 6 | 177044 |
| 7 | 1696572 |
| 8 | 17148916 |
| 9 | 182114972 |
| 10 | 2024979604 |
| 11 | 23506175868 |
| 12 | 284125820724 |
| 13 | 3567957972316 |
| 14 | 46454893734612 |
| 15 | 625979771144764 |
| 16 | 8715626185644916 |
| 17 | 125200337417147932 |
| 18 | 1853095248414187796 |
| 19 | 28225529312569364732 |
| 20 | 441925530173009732532 |
[1,6,40,292,2308,19580,177044,1696572,17148916, 182114972,2024979604,23506175868,284125820724, 3567957972316,46454893734612,625979771144764, 8715626185644916,125200337417147932, 1853095248414187796,28225529312569364732, 441925530173009732532] |