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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 10 |
| 2 | 55 |
| 3 | 385 |
| 4 | 2530 |
| 5 | 17017 |
| 6 | 113641 |
| 7 | 760804 |
| 8 | 5089282 |
| 9 | 34053437 |
| 10 | 227837533 |
| 11 | 1524414737 |
| 12 | 10199443436 |
| 13 | 68241935348 |
| 14 | 456589252304 |
| 15 | 3054922560820 |
| 16 | 20439707165252 |
| 17 | 136756870048981 |
| 18 | 915005341022187 |
| 19 | 6122067418010887 |
| 20 | 40961191948244094 |
| 21 | 274060890253820561 |
[1,10,55,385,2530,17017,113641,760804,5089282, 34053437,227837533,1524414737,10199443436, 68241935348,456589252304,3054922560820, 20439707165252,136756870048981,915005341022187, 6122067418010887,40961191948244094, 274060890253820561] |