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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 23 |
| 3 | 15 |
| 4 | 2355 |
| 5 | 1395 |
| 6 | 102971 |
| 7 | 58331 |
| 8 | 16664147 |
| 9 | 9197779 |
| 10 | 160882675 |
| 11 | 87300443 |
| 12 | 48181451689 |
| 13 | 25832538281 |
| 14 | 881993826001 |
| 15 | 468673213505 |
| 16 | 508090131646771 |
| 17 | 268129446332211 |
| 18 | 4514206380211785 |
| 19 | 2369170809554097 |
| 20 | 317528931045821675 |
[1,2,23,15,2355,1395,102971,58331,16664147, 9197779,160882675,87300443,48181451689, 25832538281,881993826001,468673213505, 508090131646771,268129446332211,4514206380211785, 2369170809554097,317528931045821675] |