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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 19 |
| 4 | 66 |
| 5 | 249 |
| 6 | 996 |
| 7 | 4148 |
| 8 | 17784 |
| 9 | 77939 |
| 10 | 347516 |
| 11 | 1571304 |
| 12 | 7187288 |
| 13 | 33196887 |
| 14 | 154611392 |
| 15 | 725284721 |
| 16 | 3423760262 |
| 17 | 16251813715 |
| 18 | 77523741208 |
| 19 | 371428985796 |
| 20 | 1786623827240 |
| 21 | 8624669381161 |
| 22 | 41769772877288 |
| 23 | 202893913979291 |
| 24 | 988224403828490 |
| 25 | 4825331506973445 |
[1,2,6,19,66,249,996,4148,17784,77939,347516, 1571304,7187288,33196887,154611392,725284721, 3423760262,16251813715,77523741208,371428985796, 1786623827240,8624669381161,41769772877288, 202893913979291,988224403828490,4825331506973445] |