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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 9 |
| 3 | 57 |
| 4 | 396 |
| 5 | 2948 |
| 6 | 23016 |
| 7 | 185838 |
| 8 | 1539066 |
| 9 | 13001677 |
| 10 | 111600446 |
| 11 | 970550862 |
| 12 | 8533427593 |
| 13 | 75728797781 |
| 14 | 677427655798 |
| 15 | 6102015206945 |
| 16 | 55299451023428 |
| 17 | 503847366381836 |
| 18 | 4612663920303329 |
| 19 | 42409513650507927 |
| 20 | 391425863599784588 |
[1,2,9,57,396,2948,23016,185838,1539066,13001677, 111600446,970550862,8533427593,75728797781, 677427655798,6102015206945,55299451023428, 503847366381836,4612663920303329, 42409513650507927,391425863599784588] |