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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 18 |
| 3 | 135 |
| 4 | 1134 |
| 5 | 10206 |
| 6 | 96228 |
| 7 | 938223 |
| 8 | 9382230 |
| 9 | 95698746 |
| 10 | 991787004 |
| 11 | 10413763542 |
| 12 | 110546105292 |
| 13 | 1184422556700 |
| 14 | 12791763612360 |
| 15 | 139110429284415 |
| 16 | 1522031755700070 |
| 17 | 16742349312700770 |
| 18 | 185047018719324300 |
| 19 | 2054021907784499730 |
| 20 | 22887672686741568420 |
| 21 | 255925794588110265060 |
[1,3,18,135,1134,10206,96228,938223,9382230, 95698746,991787004,10413763542,110546105292, 1184422556700,12791763612360,139110429284415, 1522031755700070,16742349312700770, 185047018719324300,2054021907784499730, 22887672686741568420,255925794588110265060] |