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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 21 |
| 2 | 903 |
| 3 | 49525 |
| 4 | 3070308 |
| 5 | 204928371 |
| 6 | 14369906538 |
| 7 | 1043861319189 |
| 8 | 77866470852108 |
| 9 | 5929621690613108 |
| 10 | 459076176165983247 |
| 11 | 36026517938705145267 |
| 12 | 2859318461620989381900 |
| 13 | 229114879928544260792946 |
| 14 | 18509862380800289696106372 |
| 15 | 1506048000721264678984095445 |
| 16 | 123303480420582227597300406588 |
[1,21,903,49525,3070308,204928371,14369906538, 1043861319189,77866470852108,5929621690613108, 459076176165983247,36026517938705145267, 2859318461620989381900,229114879928544260792946, 18509862380800289696106372, 1506048000721264678984095445, 123303480420582227597300406588] |