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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 31 |
| 4 | 362 |
| 5 | 5567 |
| 6 | 104229 |
| 7 | 2268586 |
| 8 | 55817457 |
| 9 | 1524956611 |
| 10 | 45699911560 |
| 11 | 1489007130546 |
| 12 | 52390324106713 |
| 13 | 1979726546053502 |
| 14 | 79978929224189504 |
| 15 | 3440756672193895992 |
| 16 | 157085559415640319126 |
| 17 | 7587124626671398460006 |
| 18 | 386598739562989187413005 |
| 19 | 20728976430148069600767400 |
| 20 | 1166849728839227202686314988 |
[1,1,4,31,362,5567,104229,2268586,55817457, 1524956611,45699911560,1489007130546, 52390324106713,1979726546053502,79978929224189504, 3440756672193895992,157085559415640319126, 7587124626671398460006,386598739562989187413005, 20728976430148069600767400, 1166849728839227202686314988] |