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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 20 |
| 6 | 45 |
| 7 | 101 |
| 8 | 228 |
| 9 | 515 |
| 10 | 1164 |
| 11 | 2631 |
| 12 | 5947 |
| 13 | 13443 |
| 14 | 30388 |
| 15 | 68694 |
| 16 | 155287 |
| 17 | 351036 |
| 18 | 793541 |
| 19 | 1793853 |
| 20 | 4055128 |
| 21 | 9166895 |
| 22 | 20722396 |
| 23 | 46844400 |
| 24 | 105894986 |
| 25 | 239382894 |
| 26 | 541141486 |
| 27 | 1223287525 |
| 28 | 2765325535 |
| 29 | 6251208451 |
| 30 | 14131286391 |
[1,1,2,4,9,20,45,101,228,515,1164,2631,5947,13443, 30388,68694,155287,351036,793541,1793853,4055128, 9166895,20722396,46844400,105894986,239382894, 541141486,1223287525,2765325535,6251208451, 14131286391] |