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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 6 |
| 3 | 15 |
| 4 | 37 |
| 5 | 94 |
| 6 | 241 |
| 7 | 623 |
| 8 | 1618 |
| 9 | 4215 |
| 10 | 11001 |
| 11 | 28746 |
| 12 | 75169 |
| 13 | 196651 |
| 14 | 514606 |
| 15 | 1346879 |
| 16 | 3525565 |
| 17 | 9229062 |
| 18 | 24160401 |
| 19 | 63250167 |
| 20 | 165586906 |
| 21 | 433505383 |
| 22 | 1134920881 |
| 23 | 2971243730 |
| 24 | 7778788417 |
| 25 | 20365086099 |
| 26 | 53316412566 |
| 27 | 139584058863 |
[1,3,6,15,37,94,241,623,1618,4215,11001,28746, 75169,196651,514606,1346879,3525565,9229062, 24160401,63250167,165586906,433505383,1134920881, 2971243730,7778788417,20365086099,53316412566, 139584058863] |