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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 5 |
| 3 | 17 |
| 4 | 74 |
| 5 | 395 |
| 6 | 2526 |
| 7 | 19087 |
| 8 | 168603 |
| 9 | 1723065 |
| 10 | 20148031 |
| 11 | 266437102 |
| 12 | 3938754720 |
| 13 | 64391209604 |
| 14 | 1152961464743 |
| 15 | 22424127879610 |
| 16 | 470399253269776 |
| 17 | 10579865622308851 |
| 18 | 253840801521314095 |
| 19 | 6468953273455413674 |
| 20 | 174452533187403980841 |
| 21 | 4962228907578051232358 |
[1,2,5,17,74,395,2526,19087,168603,1723065, 20148031,266437102,3938754720,64391209604, 1152961464743,22424127879610,470399253269776, 10579865622308851,253840801521314095, 6468953273455413674,174452533187403980841, 4962228907578051232358] |