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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 19 |
| 3 | 140 |
| 4 | 1206 |
| 5 | 10020 |
| 6 | 84160 |
| 7 | 705156 |
| 8 | 5912277 |
| 9 | 49563492 |
| 10 | 415515336 |
| 11 | 3483440165 |
| 12 | 29203220338 |
| 13 | 244823382148 |
| 14 | 2052461910954 |
| 15 | 17206688780344 |
| 16 | 144251223226490 |
| 17 | 1209321306131007 |
| 18 | 10138271200549217 |
| 19 | 84993576475914931 |
| 20 | 712538449541938001 |
[1,19,140,1206,10020,84160,705156,5912277, 49563492,415515336,3483440165,29203220338, 244823382148,2052461910954,17206688780344, 144251223226490,1209321306131007, 10138271200549217,84993576475914931, 712538449541938001] |