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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 10 |
| 4 | 38 |
| 5 | 132 |
| 6 | 487 |
| 7 | 1862 |
| 8 | 7245 |
| 9 | 28422 |
| 10 | 113605 |
| 11 | 457643 |
| 12 | 1859672 |
| 13 | 7605699 |
| 14 | 31310991 |
| 15 | 129568364 |
| 16 | 538485313 |
| 17 | 2246892203 |
| 18 | 9410626846 |
| 19 | 39534850340 |
| 20 | 166557012942 |
| 21 | 703547733280 |
| 22 | 2978832014892 |
| 23 | 12638990514849 |
| 24 | 53732382345325 |
| 25 | 228850861814858 |
| 26 | 976318372408322 |
| 27 | 4171575158414500 |
[1,1,4,10,38,132,487,1862,7245,28422,113605, 457643,1859672,7605699,31310991,129568364, 538485313,2246892203,9410626846,39534850340, 166557012942,703547733280,2978832014892, 12638990514849,53732382345325,228850861814858, 976318372408322,4171575158414500] |