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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 270 |
| 3 | 2871 |
| 4 | 18171 |
| 5 | 89991 |
| 6 | 375741 |
| 7 | 1380456 |
| 8 | 4602852 |
| 9 | 14210922 |
| 10 | 41167332 |
| 11 | 112987953 |
| 12 | 296065548 |
| 13 | 745155153 |
| 14 | 1809970083 |
| 15 | 4259274975 |
| 16 | 9741874320 |
| 17 | 21715729830 |
| 18 | 47285705676 |
| 19 | 100777629492 |
| 20 | 210581716518 |
| 21 | 432065232288 |
| 22 | 871606268064 |
| 23 | 1730764182321 |
| 24 | 3386501211393 |
[1,0,270,2871,18171,89991,375741,1380456,4602852, 14210922,41167332,112987953,296065548,745155153, 1809970083,4259274975,9741874320,21715729830, 47285705676,100777629492,210581716518, 432065232288,871606268064,1730764182321, 3386501211393] |