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| n | a(n) |
|---|---|
| 1 | 20 |
| 2 | 76 |
| 3 | 285 |
| 4 | 1065 |
| 5 | 3976 |
| 6 | 14840 |
| 7 | 55385 |
| 8 | 206701 |
| 9 | 771420 |
| 10 | 2878980 |
| 11 | 10744501 |
| 12 | 40099025 |
| 13 | 149651600 |
| 14 | 558507376 |
| 15 | 2084377905 |
| 16 | 7779004245 |
| 17 | 29031639076 |
| 18 | 108347552060 |
| 19 | 404358569165 |
| 20 | 1509086724601 |
| 21 | 5631988329240 |
| 22 | 21018866592360 |
| 23 | 78443478040201 |
| 24 | 292755045568445 |
[20,76,285,1065,3976,14840,55385,206701,771420, 2878980,10744501,40099025,149651600,558507376, 2084377905,7779004245,29031639076,108347552060, 404358569165,1509086724601,5631988329240, 21018866592360,78443478040201,292755045568445] |