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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 7 |
| 3 | 12 |
| 4 | 73 |
| 5 | 216 |
| 6 | 919 |
| 7 | 3204 |
| 8 | 12409 |
| 9 | 45408 |
| 10 | 171271 |
| 11 | 635580 |
| 12 | 2379241 |
| 13 | 8865000 |
| 14 | 33113527 |
| 15 | 123523572 |
| 16 | 461111833 |
| 17 | 1720661616 |
| 18 | 6422058919 |
| 19 | 23966525484 |
| 20 | 89446140169 |
| 21 | 333813840888 |
| 22 | 1245817611991 |
| 23 | 4649439829860 |
| 24 | 17351975261881 |
| 25 | 64758394108800 |
| 26 | 241681735391047 |
[1,0,7,12,73,216,919,3204,12409,45408,171271, 635580,2379241,8865000,33113527,123523572, 461111833,1720661616,6422058919,23966525484, 89446140169,333813840888,1245817611991, 4649439829860,17351975261881,64758394108800, 241681735391047] |