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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 16 |
| 5 | 56 |
| 6 | 218 |
| 7 | 937 |
| 8 | 4376 |
| 9 | 22027 |
| 10 | 118744 |
| 11 | 681570 |
| 12 | 4144988 |
| 13 | 26598313 |
| 14 | 179451366 |
| 15 | 1268930969 |
| 16 | 9378332608 |
| 17 | 72267300476 |
| 18 | 579336907254 |
| 19 | 4822070246225 |
| 20 | 41597773001612 |
| 21 | 371306237988959 |
| 22 | 3424303740576440 |
| 23 | 32583334570211654 |
| 24 | 319487530199710232 |
| 25 | 3224337031346853361 |
[0,1,2,5,16,56,218,937,4376,22027,118744,681570, 4144988,26598313,179451366,1268930969,9378332608, 72267300476,579336907254,4822070246225, 41597773001612,371306237988959,3424303740576440, 32583334570211654,319487530199710232, 3224337031346853361] |