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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 7 |
| 4 | 49 |
| 5 | 241 |
| 6 | 2041 |
| 7 | 26041 |
| 8 | 282913 |
| 9 | 3449377 |
| 10 | 57170161 |
| 11 | 973059121 |
| 12 | 16847893921 |
| 13 | 343341027745 |
| 14 | 7680743819113 |
| 15 | 175958943331081 |
| 16 | 4375517632543681 |
| 17 | 118932887426911681 |
| 18 | 3374685950589927649 |
| 19 | 100735118425384221025 |
| 20 | 3217474234925998764481 |
[1,1,1,7,49,241,2041,26041,282913,3449377, 57170161,973059121,16847893921,343341027745, 7680743819113,175958943331081,4375517632543681, 118932887426911681,3374685950589927649, 100735118425384221025,3217474234925998764481] |