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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 30 |
| 4 | 126 |
| 5 | 534 |
| 6 | 2262 |
| 7 | 9534 |
| 8 | 40254 |
| 9 | 169302 |
| 10 | 702510 |
| 11 | 2929806 |
| 12 | 12222414 |
| 13 | 50908158 |
| 14 | 212134902 |
| 15 | 882794118 |
| 16 | 3654001326 |
| 17 | 15159263934 |
| 18 | 62906444238 |
| 19 | 260853828438 |
| 20 | 1081924309806 |
| 21 | 4484440327350 |
[1,6,30,126,534,2262,9534,40254,169302,702510, 2929806,12222414,50908158,212134902,882794118, 3654001326,15159263934,62906444238,260853828438, 1081924309806,4484440327350] |