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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 31 |
| 4 | 164 |
| 5 | 999 |
| 6 | 6841 |
| 7 | 51790 |
| 8 | 428131 |
| 9 | 3827967 |
| 10 | 36738144 |
| 11 | 376118747 |
| 12 | 4086419601 |
| 13 | 46910207114 |
| 14 | 566845074703 |
| 15 | 7186474088735 |
| 16 | 95318816501420 |
| 17 | 1319330556537631 |
| 18 | 19013488408858761 |
| 19 | 284724852032757686 |
| 20 | 4422344774431494155 |
| 21 | 71125541977466879231 |
[1,2,7,31,164,999,6841,51790,428131,3827967, 36738144,376118747,4086419601,46910207114, 566845074703,7186474088735,95318816501420, 1319330556537631,19013488408858761, 284724852032757686,4422344774431494155, 71125541977466879231] |