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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 22 |
| 4 | 132 |
| 5 | 890 |
| 6 | 6812 |
| 7 | 58422 |
| 8 | 555900 |
| 9 | 5819658 |
| 10 | 66554180 |
| 11 | 825839718 |
| 12 | 11054124886 |
| 13 | 158795559000 |
| 14 | 2437248222710 |
| 15 | 39809464449676 |
| 16 | 689538524084168 |
| 17 | 12625142440334342 |
| 18 | 243656361772961292 |
| 19 | 4943801229819987022 |
| 20 | 105212500452414418118 |
| 21 | 2343513475564027153128 |
[1,4,22,132,890,6812,58422,555900,5819658, 66554180,825839718,11054124886,158795559000, 2437248222710,39809464449676,689538524084168, 12625142440334342,243656361772961292, 4943801229819987022,105212500452414418118, 2343513475564027153128] |