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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 14 |
| 4 | 87 |
| 5 | 608 |
| 6 | 5573 |
| 7 | 57876 |
| 8 | 687938 |
| 9 | 9058892 |
| 10 | 130851823 |
| 11 | 2048654450 |
| 12 | 34488422057 |
| 13 | 620046639452 |
| 14 | 11839393796270 |
| 15 | 238984150459124 |
| 16 | 5079583100918338 |
| 17 | 113299159314626360 |
| 18 | 2644085918303683758 |
| 19 | 64393240540265515110 |
| 20 | 1632731130253043991252 |
| 21 | 43013015553755764179000 |
[1,4,14,87,608,5573,57876,687938,9058892, 130851823,2048654450,34488422057,620046639452, 11839393796270,238984150459124,5079583100918338, 113299159314626360,2644085918303683758, 64393240540265515110,1632731130253043991252, 43013015553755764179000] |