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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 18 |
| 3 | 294 |
| 4 | 7136 |
| 5 | 231410 |
| 6 | 9421932 |
| 7 | 462459242 |
| 8 | 26593896912 |
| 9 | 1754278123266 |
| 10 | 130611457831700 |
| 11 | 10835721949072922 |
| 12 | 991315043401627320 |
| 13 | 99154012317212577218 |
| 14 | 10765112531819005907484 |
| 15 | 1260860266373297376720810 |
| 16 | 158473050112495481401395872 |
| 17 | 21275613503385328981848681986 |
[1,2,18,294,7136,231410,9421932,462459242, 26593896912,1754278123266,130611457831700, 10835721949072922,991315043401627320, 99154012317212577218,10765112531819005907484, 1260860266373297376720810, 158473050112495481401395872, 21275613503385328981848681986] |