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| n | a(n) |
|---|---|
| 3 | 1 |
| 4 | 15 |
| 5 | 144 |
| 6 | 1137 |
| 7 | 8070 |
| 8 | 53678 |
| 9 | 342224 |
| 10 | 2119359 |
| 11 | 12856752 |
| 12 | 76826324 |
| 13 | 453947206 |
| 14 | 2659486160 |
| 15 | 15479103062 |
| 16 | 89636939038 |
| 17 | 517014933254 |
| 18 | 2972784038825 |
| 19 | 17051188983758 |
| 20 | 97611767361074 |
| 21 | 557935896092592 |
| 22 | 3185250335024206 |
[1,15,144,1137,8070,53678,342224,2119359,12856752, 76826324,453947206,2659486160,15479103062, 89636939038,517014933254,2972784038825, 17051188983758,97611767361074,557935896092592, 3185250335024206] |