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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 30 |
| 3 | 204 |
| 4 | 1014 |
| 5 | 5716 |
| 6 | 31212 |
| 7 | 163480 |
| 8 | 826278 |
| 9 | 4320132 |
| 10 | 22096324 |
| 11 | 110079016 |
| 12 | 552324796 |
| 13 | 2721379144 |
| 14 | 13415146648 |
| 15 | 66143801648 |
| 16 | 321016593670 |
| 17 | 1549027853156 |
| 18 | 7506317522132 |
| 19 | 35931754574216 |
| 20 | 171790455469140 |
| 21 | 820584857999448 |
| 22 | 3893605676834920 |
| 23 | 18400781049682512 |
[1,6,30,204,1014,5716,31212,163480,826278,4320132, 22096324,110079016,552324796,2721379144, 13415146648,66143801648,321016593670, 1549027853156,7506317522132,35931754574216, 171790455469140,820584857999448,3893605676834920, 18400781049682512] |