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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 21 |
| 3 | 41 |
| 4 | 117 |
| 5 | 316 |
| 6 | 810 |
| 7 | 2208 |
| 8 | 6012 |
| 9 | 15837 |
| 10 | 42579 |
| 11 | 115618 |
| 12 | 309144 |
| 13 | 829935 |
| 14 | 2246106 |
| 15 | 6045980 |
| 16 | 16264045 |
| 17 | 43945153 |
| 18 | 118607081 |
| 19 | 319754491 |
| 20 | 863718047 |
| 21 | 2333646132 |
| 22 | 6300949455 |
| 23 | 17025299379 |
| 24 | 46023642233 |
| 25 | 124382811126 |
| 26 | 336236258224 |
[4,21,41,117,316,810,2208,6012,15837,42579,115618, 309144,829935,2246106,6045980,16264045,43945153, 118607081,319754491,863718047,2333646132, 6300949455,17025299379,46023642233,124382811126, 336236258224] |