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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 18 |
| 2 | 170 |
| 3 | 1122 |
| 4 | 5813 |
| 5 | 25176 |
| 6 | 94791 |
| 7 | 318630 |
| 8 | 974643 |
| 9 | 2752112 |
| 10 | 7253764 |
| 11 | 18003544 |
| 12 | 42378246 |
| 13 | 95162260 |
| 14 | 204856291 |
| 15 | 424515042 |
| 16 | 849825768 |
| 17 | 1648470894 |
| 18 | 3106669575 |
| 19 | 5701318544 |
| 20 | 10209535182 |
| 21 | 17871860844 |
| 22 | 30631158960 |
| 23 | 51476623220 |
| 24 | 84931612739 |
[1,18,170,1122,5813,25176,94791,318630,974643, 2752112,7253764,18003544,42378246,95162260, 204856291,424515042,849825768,1648470894, 3106669575,5701318544,10209535182,17871860844, 30631158960,51476623220,84931612739] |