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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 24 |
| 6 | 75 |
| 7 | 269 |
| 8 | 1091 |
| 9 | 4940 |
| 10 | 24699 |
| 11 | 135141 |
| 12 | 803122 |
| 13 | 5150259 |
| 14 | 35436569 |
| 15 | 260300079 |
| 16 | 2032260757 |
| 17 | 16798435176 |
| 18 | 146498077799 |
| 19 | 1343752561687 |
| 20 | 12927673809234 |
| 21 | 130120187348654 |
| 22 | 1367117984143960 |
| 23 | 14962669807495136 |
[1,1,2,4,9,24,75,269,1091,4940,24699,135141, 803122,5150259,35436569,260300079,2032260757, 16798435176,146498077799,1343752561687, 12927673809234,130120187348654,1367117984143960, 14962669807495136] |