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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 13 |
| 5 | 35 |
| 6 | 120 |
| 7 | 392 |
| 8 | 1405 |
| 9 | 4998 |
| 10 | 18378 |
| 11 | 67792 |
| 12 | 253509 |
| 13 | 952534 |
| 14 | 3604624 |
| 15 | 13699554 |
| 16 | 52304807 |
| 17 | 200406370 |
| 18 | 770442286 |
| 19 | 2970401696 |
| 20 | 11482513428 |
| 21 | 44491881033 |
| 22 | 172766765654 |
| 23 | 672186650116 |
| 24 | 2619996250930 |
| 25 | 10228902882021 |
| 26 | 39996345469572 |
| 27 | 156612023354364 |
| 28 | 614044364443761 |
[1,2,4,13,35,120,392,1405,4998,18378,67792,253509, 952534,3604624,13699554,52304807,200406370, 770442286,2970401696,11482513428,44491881033, 172766765654,672186650116,2619996250930, 10228902882021,39996345469572,156612023354364, 614044364443761] |