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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 6 |
| 5 | 10 |
| 6 | 20 |
| 7 | 56 |
| 8 | 168 |
| 9 | 456 |
| 10 | 1137 |
| 11 | 2827 |
| 12 | 7458 |
| 13 | 20670 |
| 14 | 57577 |
| 15 | 157691 |
| 16 | 427976 |
| 17 | 1170552 |
| 18 | 3248411 |
| 19 | 9096497 |
| 20 | 25505562 |
| 21 | 71436182 |
| 22 | 200338074 |
| 23 | 564083786 |
| 24 | 1595055520 |
| 25 | 4522769520 |
| 26 | 12842772295 |
| 27 | 36514010301 |
| 28 | 103995490758 |
| 29 | 296794937626 |
| 30 | 848620165860 |
| 31 | 2430089817720 |
[0,0,1,3,6,10,20,56,168,456,1137,2827,7458,20670, 57577,157691,427976,1170552,3248411,9096497, 25505562,71436182,200338074,564083786,1595055520, 4522769520,12842772295,36514010301,103995490758, 296794937626,848620165860,2430089817720] |