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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 9 |
| 3 | 40 |
| 4 | 184 |
| 5 | 872 |
| 6 | 4232 |
| 7 | 20936 |
| 8 | 105208 |
| 9 | 535624 |
| 10 | 2757000 |
| 11 | 14324456 |
| 12 | 75028152 |
| 13 | 395750568 |
| 14 | 2100380424 |
| 15 | 11208429960 |
| 16 | 60103977976 |
| 17 | 323708642952 |
| 18 | 1750294676744 |
| 19 | 9497584905128 |
| 20 | 51703651336888 |
| 21 | 282302043458536 |
| 22 | 1545558070957960 |
| 23 | 8482843567140680 |
[1,2,9,40,184,872,4232,20936,105208,535624, 2757000,14324456,75028152,395750568,2100380424, 11208429960,60103977976,323708642952, 1750294676744,9497584905128,51703651336888, 282302043458536,1545558070957960,8482843567140680] |