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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 22 |
| 3 | 130 |
| 4 | 789 |
| 5 | 4848 |
| 6 | 29975 |
| 7 | 185953 |
| 8 | 1155696 |
| 9 | 7190013 |
| 10 | 44757663 |
| 11 | 278707048 |
| 12 | 1735840329 |
| 13 | 10812295670 |
| 14 | 67352305826 |
| 15 | 419567747884 |
| 16 | 2613727621445 |
| 17 | 16282589303341 |
| 18 | 101435368987532 |
| 19 | 631912517383722 |
| 20 | 3936637423973502 |
| 21 | 24524174461033569 |
| 22 | 152779004164967032 |
[1,4,22,130,789,4848,29975,185953,1155696,7190013, 44757663,278707048,1735840329,10812295670, 67352305826,419567747884,2613727621445, 16282589303341,101435368987532,631912517383722, 3936637423973502,24524174461033569, 152779004164967032] |