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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 21 |
| 2 | 169 |
| 3 | 1401 |
| 4 | 11729 |
| 5 | 98733 |
| 6 | 833745 |
| 7 | 7053777 |
| 8 | 59744071 |
| 9 | 506355371 |
| 10 | 4293250829 |
| 11 | 36409762185 |
| 12 | 308822547173 |
| 13 | 2619602438143 |
| 14 | 22221971988277 |
| 15 | 188513351680519 |
| 16 | 1599222568187231 |
| 17 | 13566880665362081 |
| 18 | 115094253790715069 |
[1,21,169,1401,11729,98733,833745,7053777, 59744071,506355371,4293250829,36409762185, 308822547173,2619602438143,22221971988277, 188513351680519,1599222568187231, 13566880665362081,115094253790715069] |