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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 32 |
| 5 | 162 |
| 6 | 813 |
| 7 | 4068 |
| 8 | 20344 |
| 9 | 101724 |
| 10 | 508625 |
| 11 | 2543130 |
| 12 | 12715656 |
| 13 | 63578286 |
| 14 | 317891437 |
| 15 | 1589457192 |
| 16 | 7947285968 |
| 17 | 39736429848 |
| 18 | 198682149249 |
| 19 | 993410746254 |
| 20 | 4967053731280 |
| 21 | 24835268656410 |
| 22 | 124176343282061 |
| 23 | 620881716410316 |
[0,0,1,6,32,162,813,4068,20344,101724,508625, 2543130,12715656,63578286,317891437,1589457192, 7947285968,39736429848,198682149249,993410746254, 4967053731280,24835268656410,124176343282061, 620881716410316] |