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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 7 |
| 3 | 7 |
| 4 | 91 |
| 5 | 217 |
| 6 | 1561 |
| 7 | 5593 |
| 8 | 32011 |
| 9 | 139363 |
| 10 | 732697 |
| 11 | 3492265 |
| 12 | 17899609 |
| 13 | 89014933 |
| 14 | 455041825 |
| 15 | 2311847083 |
| 16 | 11875575355 |
| 17 | 61080825757 |
[1,0,7,7,91,217,1561,5593,32011,139363,732697, 3492265,17899609,89014933,455041825,2311847083, 11875575355,61080825757] |