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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 9 |
| 4 | 18 |
| 5 | 162 |
| 6 | 261 |
| 7 | 4376 |
| 8 | 19712 |
| 9 | 32805 |
| 10 | 65610 |
| 11 | 131220 |
| 12 | 4785156 |
| 13 | 9570312 |
| 14 | 272629962 |
| 15 | 1208614932 |
| 16 | 2542645806624 |
| 17 | 154206526918656 |
| 18 | 2348694485729280 |
| 19 | 9341451062288388 |
| 20 | 18049789376104448 |
| 21 | 451521135633235968 |
[1,6,9,18,162,261,4376,19712,32805,65610,131220, 4785156,9570312,272629962,1208614932, 2542645806624,154206526918656,2348694485729280, 9341451062288388,18049789376104448, 451521135633235968] |