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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 23 |
| 3 | 56 |
| 4 | 168 |
| 5 | 459 |
| 6 | 1080 |
| 7 | 2400 |
| 8 | 5461 |
| 9 | 12678 |
| 10 | 28728 |
| 11 | 63336 |
| 12 | 138717 |
| 13 | 303346 |
| 14 | 663179 |
| 15 | 1438098 |
| 16 | 3062730 |
| 17 | 6450121 |
| 18 | 13583957 |
| 19 | 28627773 |
| 20 | 59954459 |
| 21 | 124413466 |
| 22 | 258510987 |
| 23 | 543867101 |
| 24 | 1152248068 |
| 25 | 2428235533 |
| 26 | 5069886692 |
| 27 | 10511339217 |
| 28 | 21696371682 |
| 29 | 44710463120 |
[1,6,23,56,168,459,1080,2400,5461,12678,28728, 63336,138717,303346,663179,1438098,3062730, 6450121,13583957,28627773,59954459,124413466, 258510987,543867101,1152248068,2428235533, 5069886692,10511339217,21696371682,44710463120] |