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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 15 |
| 6 | 59 |
| 7 | 187 |
| 8 | 533 |
| 9 | 1541 |
| 10 | 4893 |
| 11 | 16797 |
| 12 | 58663 |
| 13 | 201347 |
| 14 | 679767 |
| 15 | 2294967 |
| 16 | 7850121 |
| 17 | 27247369 |
| 18 | 95375225 |
| 19 | 334643225 |
| 20 | 1174649611 |
| 21 | 4129971863 |
| 22 | 14570334995 |
| 23 | 51610458291 |
| 24 | 183436895645 |
| 25 | 653582527693 |
| 26 | 2333035219285 |
| 27 | 8342630973365 |
[1,1,1,1,3,15,59,187,533,1541,4893,16797,58663, 201347,679767,2294967,7850121,27247369,95375225, 334643225,1174649611,4129971863,14570334995, 51610458291,183436895645,653582527693, 2333035219285,8342630973365] |