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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 15 |
| 2 | 159 |
| 3 | 1460 |
| 4 | 12405 |
| 5 | 100449 |
| 6 | 787390 |
| 7 | 6030240 |
| 8 | 45386460 |
| 9 | 337036980 |
| 10 | 2476230876 |
| 11 | 18036064140 |
| 12 | 130431953357 |
| 13 | 937603882245 |
| 14 | 6705639192060 |
| 15 | 47748355535600 |
| 16 | 338708562711465 |
| 17 | 2394692570004255 |
| 18 | 16881072760978035 |
| 19 | 118691594469460080 |
| 20 | 832588258306289580 |
| 21 | 5828191882336453020 |
[1,15,159,1460,12405,100449,787390,6030240, 45386460,337036980,2476230876,18036064140, 130431953357,937603882245,6705639192060, 47748355535600,338708562711465,2394692570004255, 16881072760978035,118691594469460080, 832588258306289580,5828191882336453020] |