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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 9 |
| 4 | 25 |
| 5 | 89 |
| 6 | 403 |
| 7 | 2246 |
| 8 | 14887 |
| 9 | 114239 |
| 10 | 994909 |
| 11 | 9687123 |
| 12 | 104223700 |
| 13 | 1227484193 |
| 14 | 15703071262 |
| 15 | 216798771109 |
| 16 | 3212441188268 |
| 17 | 50845473960657 |
| 18 | 856063393693256 |
| 19 | 15276025334127835 |
| 20 | 287977916632275512 |
[1,2,4,9,25,89,403,2246,14887,114239,994909, 9687123,104223700,1227484193,15703071262, 216798771109,3212441188268,50845473960657, 856063393693256,15276025334127835, 287977916632275512] |