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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 3 |
| 4 | 10 |
| 5 | 30 |
| 6 | 90 |
| 7 | 266 |
| 8 | 783 |
| 9 | 2295 |
| 10 | 6710 |
| 11 | 19580 |
| 12 | 57057 |
| 13 | 166101 |
| 14 | 483210 |
| 15 | 1405080 |
| 16 | 4084590 |
| 17 | 11872494 |
| 18 | 34508997 |
| 19 | 100313635 |
| 20 | 291646580 |
| 21 | 848102640 |
| 22 | 2466916474 |
| 23 | 7177785582 |
| 24 | 20891443950 |
| 25 | 60827142350 |
| 26 | 177167486925 |
| 27 | 516217883571 |
| 28 | 1504692189588 |
[1,3,10,30,90,266,783,2295,6710,19580,57057, 166101,483210,1405080,4084590,11872494,34508997, 100313635,291646580,848102640,2466916474, 7177785582,20891443950,60827142350,177167486925, 516217883571,1504692189588] |