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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 10 |
| 3 | 30 |
| 4 | 87 |
| 5 | 245 |
| 6 | 676 |
| 7 | 1836 |
| 8 | 4925 |
| 9 | 13079 |
| 10 | 34446 |
| 11 | 90090 |
| 12 | 234227 |
| 13 | 605865 |
| 14 | 1560200 |
| 15 | 4002072 |
| 16 | 10230201 |
| 17 | 26069995 |
| 18 | 66251090 |
| 19 | 167941494 |
| 20 | 424753615 |
| 21 | 1072057117 |
| 22 | 2700704172 |
| 23 | 6791746500 |
| 24 | 17052595573 |
| 25 | 42752015487 |
| 26 | 107035180630 |
| 27 | 267634562754 |
| 28 | 668407232235 |
| 29 | 1667467065425 |
[1,3,10,30,87,245,676,1836,4925,13079,34446,90090, 234227,605865,1560200,4002072,10230201,26069995, 66251090,167941494,424753615,1072057117, 2700704172,6791746500,17052595573,42752015487, 107035180630,267634562754,668407232235, 1667467065425] |