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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 36 |
| 4 | 237 |
| 5 | 1926 |
| 6 | 18147 |
| 7 | 195432 |
| 8 | 2353881 |
| 9 | 31392522 |
| 10 | 459730431 |
| 11 | 7306628652 |
| 12 | 125360110917 |
| 13 | 2306819281806 |
| 14 | 45287505051867 |
| 15 | 944784879298416 |
| 16 | 20866852729885617 |
| 17 | 486315480759519762 |
| 18 | 11921919558334283511 |
| 19 | 306644867097382161972 |
| 20 | 8255584865932073325981 |
[1,2,7,36,237,1926,18147,195432,2353881,31392522, 459730431,7306628652,125360110917,2306819281806, 45287505051867,944784879298416,20866852729885617, 486315480759519762,11921919558334283511, 306644867097382161972,8255584865932073325981] |