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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 28 |
| 4 | 121 |
| 5 | 570 |
| 6 | 2911 |
| 7 | 15968 |
| 8 | 93433 |
| 9 | 580162 |
| 10 | 3806275 |
| 11 | 26284368 |
| 12 | 190415809 |
| 13 | 1442982350 |
| 14 | 11409436363 |
| 15 | 93913277608 |
| 16 | 803094241309 |
| 17 | 7121757279798 |
| 18 | 65383520552131 |
| 19 | 620517308328812 |
| 20 | 6079168380979213 |
| 21 | 61402851498255790 |
| 22 | 638674759049919079 |
| 23 | 6833589979500278700 |
[1,2,7,28,121,570,2911,15968,93433,580162,3806275, 26284368,190415809,1442982350,11409436363, 93913277608,803094241309,7121757279798, 65383520552131,620517308328812,6079168380979213, 61402851498255790,638674759049919079, 6833589979500278700] |