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| n | a(n) |
|---|---|
| 1 | 3 |
| 2 | 20 |
| 3 | 93 |
| 4 | 390 |
| 5 | 1530 |
| 6 | 5768 |
| 7 | 21142 |
| 8 | 75908 |
| 9 | 268282 |
| 10 | 936480 |
| 11 | 3236244 |
| 12 | 11091230 |
| 13 | 37747805 |
| 14 | 127710397 |
| 15 | 429872190 |
| 16 | 1440515533 |
| 17 | 4808357581 |
| 18 | 15994483255 |
| 19 | 53039715042 |
| 20 | 175399135922 |
| 21 | 578584268700 |
| 22 | 1904232092224 |
| 23 | 6254245258553 |
[3,20,93,390,1530,5768,21142,75908,268282,936480, 3236244,11091230,37747805,127710397,429872190, 1440515533,4808357581,15994483255,53039715042, 175399135922,578584268700,1904232092224, 6254245258553] |