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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 2 |
| 4 | 8 |
| 5 | 32 |
| 6 | 156 |
| 7 | 871 |
| 8 | 5292 |
| 9 | 28702 |
| 10 | 154162 |
| 11 | 845532 |
| 12 | 4662014 |
| 13 | 25579463 |
| 14 | 140098348 |
| 15 | 767973001 |
| 16 | 4212065280 |
| 17 | 23097682805 |
| 18 | 126643657272 |
| 19 | 694390484065 |
| 20 | 3807499106946 |
| 21 | 20877386149018 |
| 22 | 114474503105178 |
| 23 | 627683328355315 |
| 24 | 3441701959286326 |
| 25 | 18871492466212538 |
[1,0,2,8,32,156,871,5292,28702,154162,845532, 4662014,25579463,140098348,767973001,4212065280, 23097682805,126643657272,694390484065, 3807499106946,20877386149018,114474503105178, 627683328355315,3441701959286326, 18871492466212538] |