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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 21 |
| 3 | 76 |
| 4 | 237 |
| 5 | 1150 |
| 6 | 5171 |
| 7 | 21087 |
| 8 | 90404 |
| 9 | 396578 |
| 10 | 1708355 |
| 11 | 7449218 |
| 12 | 32620902 |
| 13 | 142305006 |
| 14 | 631289909 |
| 15 | 2796791501 |
| 16 | 12347944643 |
| 17 | 55471249739 |
| 18 | 248943488370 |
| 19 | 1113943979715 |
| 20 | 5059364261656 |
| 21 | 22973975352807 |
| 22 | 104119911318511 |
[1,21,76,237,1150,5171,21087,90404,396578,1708355, 7449218,32620902,142305006,631289909,2796791501, 12347944643,55471249739,248943488370, 1113943979715,5059364261656,22973975352807, 104119911318511] |