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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 9 |
| 3 | 54 |
| 4 | 379 |
| 5 | 2948 |
| 6 | 24736 |
| 7 | 220622 |
| 8 | 2074775 |
| 9 | 20491386 |
| 10 | 212312349 |
| 11 | 2310232488 |
| 12 | 26473612772 |
| 13 | 320735694048 |
| 14 | 4126350096188 |
| 15 | 56601987176510 |
| 16 | 830233489763775 |
| 17 | 13036492313617494 |
| 18 | 218958840306428947 |
| 19 | 3924128327446669670 |
| 20 | 74779561501535316579 |
| 21 | 1509296316416028136188 |
[1,2,9,54,379,2948,24736,220622,2074775,20491386, 212312349,2310232488,26473612772,320735694048, 4126350096188,56601987176510,830233489763775, 13036492313617494,218958840306428947, 3924128327446669670,74779561501535316579, 1509296316416028136188] |