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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 6 |
| 6 | 15 |
| 7 | 40 |
| 8 | 110 |
| 9 | 303 |
| 10 | 853 |
| 11 | 2419 |
| 12 | 6950 |
| 13 | 20110 |
| 14 | 58677 |
| 15 | 172267 |
| 16 | 508825 |
| 17 | 1510472 |
| 18 | 4504978 |
| 19 | 13491155 |
| 20 | 40554394 |
| 21 | 122318519 |
| 22 | 370075767 |
| 23 | 1122830663 |
| 24 | 3415591776 |
| 25 | 10414918850 |
| 26 | 31827804005 |
| 27 | 97464863424 |
| 28 | 299032201886 |
| 29 | 919094334980 |
| 30 | 2829593105751 |
| 31 | 8724968220133 |
| 32 | 26942517476931 |
| 33 | 83312297368383 |
[1,0,0,1,2,6,15,40,110,303,853,2419,6950,20110, 58677,172267,508825,1510472,4504978,13491155, 40554394,122318519,370075767,1122830663, 3415591776,10414918850,31827804005,97464863424, 299032201886,919094334980,2829593105751, 8724968220133,26942517476931,83312297368383] |