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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 8 |
| 5 | 20 |
| 6 | 50 |
| 7 | 126 |
| 8 | 320 |
| 9 | 816 |
| 10 | 2084 |
| 11 | 5324 |
| 12 | 13600 |
| 13 | 34736 |
| 14 | 88712 |
| 15 | 226552 |
| 16 | 578560 |
| 17 | 1477504 |
| 18 | 3773200 |
| 19 | 9635888 |
| 20 | 24607872 |
| 21 | 62842944 |
| 22 | 160486688 |
| 23 | 409846752 |
| 24 | 1046656000 |
| 25 | 2672922880 |
| 26 | 6826040896 |
| 27 | 17432165568 |
| 28 | 44517810688 |
| 29 | 113688426240 |
[0,0,1,3,8,20,50,126,320,816,2084,5324,13600, 34736,88712,226552,578560,1477504,3773200,9635888, 24607872,62842944,160486688,409846752,1046656000, 2672922880,6826040896,17432165568,44517810688, 113688426240] |