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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 8 |
| 5 | 43 |
| 6 | 196 |
| 7 | 820 |
| 8 | 3264 |
| 9 | 12597 |
| 10 | 47652 |
| 11 | 177859 |
| 12 | 657800 |
| 13 | 2417416 |
| 14 | 8844448 |
| 15 | 32256553 |
| 16 | 117378336 |
| 17 | 426440955 |
| 18 | 1547491404 |
| 19 | 5610955132 |
| 20 | 20332248992 |
| 21 | 73645557469 |
| 22 | 266668876540 |
| 23 | 965384509651 |
| 24 | 3494279574288 |
| 25 | 12646311635088 |
| 26 | 45764967830976 |
| 27 | 165605867248465 |
[0,0,0,1,8,43,196,820,3264,12597,47652,177859, 657800,2417416,8844448,32256553,117378336, 426440955,1547491404,5610955132,20332248992, 73645557469,266668876540,965384509651, 3494279574288,12646311635088,45764967830976, 165605867248465] |