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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 3 |
| 2 | 6 |
| 3 | 21 |
| 4 | 48 |
| 5 | 195 |
| 6 | 462 |
| 7 | 1917 |
| 8 | 4560 |
| 9 | 18963 |
| 10 | 45126 |
| 11 | 187701 |
| 12 | 446688 |
| 13 | 1858035 |
| 14 | 4421742 |
| 15 | 18392637 |
| 16 | 43770720 |
| 17 | 182068323 |
| 18 | 433285446 |
| 19 | 1802290581 |
| 20 | 4289083728 |
| 21 | 17840837475 |
| 22 | 42457551822 |
| 23 | 176606084157 |
| 24 | 420286434480 |
| 25 | 1748220004083 |
[0,3,6,21,48,195,462,1917,4560,18963,45126,187701, 446688,1858035,4421742,18392637,43770720, 182068323,433285446,1802290581,4289083728, 17840837475,42457551822,176606084157,420286434480, 1748220004083] |