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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 15 |
| 3 | 668 |
| 4 | 21430 |
| 5 | 539596 |
| 6 | 12335295 |
| 7 | 263171408 |
| 8 | 5359546513 |
| 9 | 105415261452 |
| 10 | 2018539085414 |
| 11 | 37834061478768 |
| 12 | 696857649181435 |
| 13 | 12649926383138654 |
| 14 | 226822585839543107 |
| 15 | 4024393321769517272 |
| 16 | 70751999489862997510 |
[0,15,668,21430,539596,12335295,263171408, 5359546513,105415261452,2018539085414, 37834061478768,696857649181435,12649926383138654, 226822585839543107,4024393321769517272, 70751999489862997510] |