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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 7 |
| 3 | 41 |
| 4 | 247 |
| 5 | 1545 |
| 6 | 9975 |
| 7 | 66057 |
| 8 | 446455 |
| 9 | 3067913 |
| 10 | 21372919 |
| 11 | 150618121 |
| 12 | 1071841271 |
| 13 | 7691763721 |
| 14 | 55600938999 |
| 15 | 404488323081 |
| 16 | 2959189475319 |
| 17 | 21757613309961 |
| 18 | 160691417776119 |
| 19 | 1191577871450121 |
| 20 | 8868160862158839 |
[1,1,7,41,247,1545,9975,66057,446455,3067913, 21372919,150618121,1071841271,7691763721, 55600938999,404488323081,2959189475319, 21757613309961,160691417776119,1191577871450121, 8868160862158839] |