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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 4 |
| 7 | 10 |
| 8 | 20 |
| 9 | 60 |
| 10 | 105 |
| 11 | 168 |
| 12 | 364 |
| 13 | 588 |
| 14 | 930 |
| 15 | 2250 |
| 16 | 3960 |
| 17 | 6820 |
| 18 | 17380 |
| 19 | 30745 |
| 20 | 52507 |
| 21 | 126763 |
| 22 | 219765 |
| 23 | 372120 |
| 24 | 898380 |
| 25 | 1572228 |
| 26 | 2702252 |
| 27 | 6619596 |
| 28 | 11666760 |
| 29 | 20167170 |
| 30 | 49146654 |
| 31 | 86461704 |
| 32 | 149465844 |
| 33 | 363087604 |
| 34 | 639438019 |
[0,0,0,0,0,4,10,20,60,105,168,364,588,930,2250, 3960,6820,17380,30745,52507,126763,219765,372120, 898380,1572228,2702252,6619596,11666760,20167170, 49146654,86461704,149465844,363087604,639438019] |