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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 12 |
| 2 | 74 |
| 3 | 460 |
| 4 | 2861 |
| 5 | 17722 |
| 6 | 109037 |
| 7 | 665020 |
| 8 | 4014521 |
| 9 | 23954342 |
| 10 | 141123193 |
| 11 | 820074040 |
| 12 | 4697137637 |
| 13 | 26504081542 |
| 14 | 147300078809 |
| 15 | 806343223508 |
| 16 | 4349380581953 |
| 17 | 23130233881414 |
| 18 | 121379963732665 |
| 19 | 629130600591920 |
| 20 | 3224186845616653 |
| 21 | 16354295398317790 |
| 22 | 82187373706636505 |
[2,12,74,460,2861,17722,109037,665020,4014521, 23954342,141123193,820074040,4697137637, 26504081542,147300078809,806343223508, 4349380581953,23130233881414,121379963732665, 629130600591920,3224186845616653, 16354295398317790,82187373706636505] |